diff --git a/Durchschnitt.rkt b/Durchschnitt.rkt
new file mode 100755
index 0000000..faf8765
--- /dev/null
+++ b/Durchschnitt.rkt
@@ -0,0 +1,7 @@
+#lang racket
+
+(define (durchschnitt lst) (
+    / (apply + lst) (length lst)
+))
+
+(durchschnitt (list 1 1 1 3 3 3))
\ No newline at end of file
diff --git a/GUI.rkt b/GUI.rkt
new file mode 100755
index 0000000..ad1bd60
--- /dev/null
+++ b/GUI.rkt
@@ -0,0 +1,21 @@
+#lang racket/gui
+
+(require racket/gui/base)
+
+
+; Make a frame by instantiating the frame% class
+(define frame (new frame% [label "Example"]))
+ 
+; Make a static text message in the frame
+(define msg (new message% [parent frame]
+                          [label "No events so far..."]))
+ 
+; Make a button in the frame
+(new button% [parent frame]
+             [label "Click Me"]
+             ; Callback procedure for a button click:
+             [callback (lambda (button event)
+                         (send msg set-label "Button click"))])
+ 
+; Show the frame by calling its show method
+(send frame show #t)
\ No newline at end of file
diff --git a/Halloween.rkt b/Halloween.rkt
new file mode 100755
index 0000000..0f8db36
--- /dev/null
+++ b/Halloween.rkt
@@ -0,0 +1,28 @@
+;; The first three lines of this file were inserted by DrRacket. They record metadata
+;; about the language level of this file in a form that our tools can easily process.
+#reader(lib "htdp-advanced-reader.ss" "lang")((modname Halloween) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #t #t none #f () #f)))
+;; (map (lambda (x) (+ 5 x)) (list 1 2 (3))
+(define (zip list1 list2) (
+   map list list1 list2
+))
+
+(define (vec-mult list1 list2) (
+   foldr + 0 (map * list1 list2)
+))
+
+;(list "a" "b")
+;(list 1 2)
+(vec-mult (list 1 2 3) (list 4 5 6))
+
+
+;; number -> (number -> number)
+(define (z x)
+;; number -> number
+(lambda (y) (* x y)))
+
+((lambda (y) (* 3 y)) 4)
+((z 3) 4)
+
+
+
+(cond [ (= 5 7) (#t) ] [  ])
diff --git a/LinkedList.rkt b/LinkedList.rkt
new file mode 100755
index 0000000..5380c4d
--- /dev/null
+++ b/LinkedList.rkt
@@ -0,0 +1,3 @@
+#lang racket
+
+(define-struct linked-list-item item next prev)
\ No newline at end of file
diff --git a/SelectionSort.rkt b/SelectionSort.rkt
new file mode 100755
index 0000000..cc58aef
--- /dev/null
+++ b/SelectionSort.rkt
@@ -0,0 +1,13 @@
+#lang racket
+
+(define (selection-sort lst) (
+    cond
+    [(empty? lst) empty]
+    [else (cons
+        (apply min lst)
+        (selection-sort (remove (apply min lst) lst))
+    )
+    ]
+))
+
+(selection-sort (list 4 7 4 6 1 5 2 9 7))
\ No newline at end of file
diff --git a/test.bak b/test.bak
new file mode 100755
index 0000000..531d08f
--- /dev/null
+++ b/test.bak
@@ -0,0 +1,207 @@
+#lang racket
+;(define (fib n) (
+;    if (= n 0)
+;        0
+;    (
+;        if (= n 1)
+;        1
+;        (+ (fib (- n 1)) (fib (- n 2)))
+;    )
+;))
+;
+;(fib 10)
+
+
+;(define (fib n) (
+;    (cond
+;        [(= n 0) 0]
+;        [(= n 1) 1]
+;        [else
+;            (+ (fib (- n 1)) fib (- n 2))
+;        ]
+;    )
+;))
+;
+;(fib 10)
+
+;(define list1 ( list 1 2 3 4 ))
+;
+;(define (sum list) (
+;    if (empty? list)
+;        0
+;    ;else
+;    (
+;        +
+;        (first list)
+;        ( sum(rest list) )
+;    )
+;))
+;
+;(sum list1)
+
+;(define (list-with-length len) (
+;        if (= len 0)
+;            empty
+;        (
+;            cons 0 (list-with-length (- len 1) )
+;        )
+;))
+;
+;(list-with-length 10)
+
+;(filter (lambda (x) (> x 10) ) (list 0 5 10 15 20) )
+
+;(map (lambda (x) (+ x 10)) (list 0 1 2 3) )
+
+;(define (repeat fct times) (
+;    
+;))
+
+;(define-struct abc (a b))
+;
+;;; Type: abc -> list
+;;; Returns: bla bla
+;(define (foo p) (
+;    ;(
+;        if (abc? p)
+;        (
+;            if (list? (abc-b p))
+;            ;(
+;                (list (abc-a p) (abc-b p))
+;            ;)
+;            ;else
+;            ;(
+;                #f
+;            ;)
+;        )
+;        ; else
+;        #f
+;    ;)
+;))
+;
+;;(define test (make-abc ("asdf" (list 1 2 3 4))))
+;
+;(foo (make-abc 123 (list 1 2 3 4)))
+;
+;(foo 123)
+;
+;(foo (make-abc 123 1234))
+;
+
+;(define (contains-x? liste x) (
+;    cond
+;        [(list? x) #f]
+;        [(not (list? liste)) #f]
+;        [(empty? liste) #f]
+;        [
+;            (= (first liste) x)
+;            #t
+;        ]
+;        [
+;            else
+;            (contains-x? (rest liste) x)
+;        ]
+;    
+;))
+;
+;(contains-x? (list 12) (list 12 5))
+
+
+;(define (contains-x? liste x) (
+;    cond
+;        [(list? x) #f]
+;        [(not (list? liste)) #f]
+;        [(empty? liste) #f]
+;        [
+;            (= (first liste) x)
+;            #t
+;        ]
+;        [
+;            else
+;            (contains-x? (rest liste) x)
+;        ]
+;    
+;))
+;
+;(define (duplicate? lst) (
+;    cond
+;        [(not (list? lst)) #f]
+;        [(empty? lst) #f]
+;        [
+;            (contains-x? (rest lst) (first lst))
+;            #t
+;        ]
+;        [
+;            else
+;            (duplicate? (rest lst))
+;        ]
+;))
+;
+;(duplicate? (list 1 2 3 4 5 6 7 3))
+
+
+;(define (contains-x? liste x) (
+;    cond
+;        [(list? x) #f]
+;        [(not (list? liste)) #f]
+;        [(empty? liste) #f]
+;        [
+;            (= (first liste) x)
+;            #t
+;        ]
+;        [
+;            else
+;            (contains-x? (rest liste) x)
+;        ]
+;    
+;))
+;
+;(define (duplicate? lst) (
+;    cond
+;        [(not (list? lst)) #f]
+;        [(empty? lst) #f]
+;        [
+;            (contains-x? (rest lst) (first lst))
+;            #t
+;        ]
+;        [
+;            else
+;            (duplicate? (rest lst))
+;        ]
+;))
+;
+;(define (collect lst oracle) (
+;    cond
+;        [(empty? lst) oracle]
+;        [
+;            else
+;            (if (list? (first lst))
+;            (collect (rest lst) (collect (first lst) oracle))
+;            (
+;                collect (rest lst) (cons (first lst) oracle)
+;            ))
+;        ]
+;))
+;
+;(collect (list 1 2 3 (list 1 4 6)) empty)
+;
+;;(define (duplicates-deep? deep-lst) (
+;;
+;;))
+;
+;
+;;; Type: ( list of ANY ) -> number
+;;; Returns: the sum of the fees of all student in the list
+;( define ( sum-of-student-fees list )
+;( my-fold
+;( lambda ( x y ) ( + x y ) )
+;0
+;( my-map
+;( lambda ( stud ) ( student-fee stud ) )
+;( my-filter ( lambda ( x ) ( student? x ) ) list ) ) ) )
+
+
+(define asdf 10)
+
+(check-expect asdf 10)
+
diff --git a/test.rkt b/test.rkt
new file mode 100755
index 0000000..0f3498d
--- /dev/null
+++ b/test.rkt
@@ -0,0 +1,295 @@
+;; The first three lines of this file were inserted by DrRacket. They record metadata
+;; about the language level of this file in a form that our tools can easily process.
+#reader(lib "htdp-advanced-reader.ss" "lang")((modname test) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #t #t none #f () #f)))
+;#lang racket
+;(define (fib n) (
+;    if (= n 0)
+;        0
+;    (
+;        if (= n 1)
+;        1
+;        (+ (fib (- n 1)) (fib (- n 2)))
+;    )
+;))
+;
+;(fib 10)
+;
+;
+;(define (fib n) (
+;    (cond
+;        [(= n 0) 0]
+;        [(= n 1) 1]
+;        [else
+;            (+ (fib (- n 1)) fib (- n 2))
+;        ]
+;    )
+;))
+;
+;(fib 10)
+
+;(define list1 ( list 1 2 3 4 ))
+;
+;(define (sum list) (
+;    if (empty? list)
+;        0
+;    ;else
+;    (
+;        +
+;        (first list)
+;        ( sum(rest list) )
+;    )
+;))
+;
+;(sum list1)
+
+;(define (list-with-length len) (
+;        if (= len 0)
+;            empty
+;        (
+;            cons 0 (list-with-length (- len 1) )
+;        )
+;))
+;
+;(list-with-length 10)
+
+;(filter (lambda (x) (> x 10) ) (list 0 5 10 15 20) )
+
+;(map (lambda (x) (+ x 10)) (list 0 1 2 3) )
+
+;(define (repeat fct times) (
+;    
+;))
+
+(define-struct abc (a b))
+
+;; Type: abc -> list
+;; Returns: bla bla
+(define (foo p) (
+    ;(
+        if (abc? p)
+        (
+            if (list? (abc-b p))
+            ;(
+                (list (abc-a p) (abc-b p))
+            ;)
+            ;else
+            ;(
+                #f
+            ;)
+        )
+        ; else
+        #f
+    ;)
+))
+;
+;Variante 2 - mit (and ... ...)
+;
+;Variante 3 - mit (cond [])
+;
+;
+;;(define test (make-abc ("asdf" (list 1 2 3 4))))
+;
+;(foo (make-abc 123 (list 1 2 3 4)))
+;
+;(foo 123)
+;
+;(foo (make-abc 123 1234))
+;
+
+;(define (contains-x? liste x) (
+;    cond
+;        [(list? x) #f]
+;        [(not (list? liste)) #f]
+;        [(empty? liste) #f]
+;        [
+;            (= (first liste) x)
+;            #t
+;        ]
+;        [
+;            else
+;            (contains-x? (rest liste) x)
+;        ]
+;    
+;))
+;
+;(contains-x? (list 12) (list 12 5))
+
+
+;(define (contains-x? liste x) (
+;    cond
+;        [(list? x) #f]
+;        [(not (list? liste)) #f]
+;        [(empty? liste) #f]
+;        [
+;            (= (first liste) x)
+;            #t
+;        ]
+;        [
+;            else
+;            (contains-x? (rest liste) x)
+;        ]
+;    
+;))
+;
+;(define (duplicate? lst) (
+;    cond
+;        [(not (list? lst)) #f]
+;        [(empty? lst) #f]
+;        [
+;            (contains-x? (rest lst) (first lst))
+;            #t
+;        ]
+;        [
+;            else
+;            (duplicate? (rest lst))
+;        ]
+;))
+;
+;(duplicate? (list 1 2 3 4 5 6 7 3))
+
+
+;(define (contains-x? liste x) (
+;    cond
+;        [(list? x) #f]
+;        [(not (list? liste)) #f]
+;        [(empty? liste) #f]
+;        [
+;            (= (first liste) x)
+;            #t
+;        ]
+;        [
+;            else
+;            (contains-x? (rest liste) x)
+;        ]
+;    
+;))
+;
+;(define (duplicate? lst) (
+;    cond
+;        [(not (list? lst)) #f]
+;        [(empty? lst) #f]
+;        [
+;            (contains-x? (rest lst) (first lst))
+;            #t
+;        ]
+;        [
+;            else
+;            (duplicate? (rest lst))
+;        ]
+;))
+;
+;(define (collect lst oracle) (
+;    cond
+;        [(empty? lst) oracle]
+;        [
+;            else
+;            (if (list? (first lst))
+;            (collect (rest lst) (collect (first lst) oracle))
+;            (
+;                collect (rest lst) (cons (first lst) oracle)
+;            ))
+;        ]
+;))
+;
+;(define (collect lst oracle) (
+;    cond
+;        [(empty? lst) oracle]
+;        [(list? (first lst)) (
+;            collect (first lst) (collect (rest list ) oracle)
+;        )]
+;        [
+;            else
+;                (collect (rest lst) (cons (first lst) oracle))
+;        ]
+;))
+;
+;(define (duplicates-deep? deep-lst) (
+;    duplicates? (collect deep-lst '())
+;))
+;
+;(collect (list 1 2 3 (list 1 4 6)) empty)
+;
+;;(define (duplicates-deep? deep-lst) (
+;;
+;;))
+;
+;
+;;; Type: ( list of ANY ) -> number
+;;; Returns: the sum of the fees of all student in the list
+;( define ( sum-of-student-fees list )
+;( my-fold
+;( lambda ( x y ) ( + x y ) )
+;0
+;( my-map
+;( lambda ( stud ) ( student-fee stud ) )
+;( my-filter ( lambda ( x ) ( student? x ) ) list ) ) ) )
+
+
+;(define asdf 10)
+;(define aaa 20)
+;
+;(define (add x y) (+ x y))
+;
+;(check-expect (add asdf asdf) aaa)
+
+;;; (define (euclid a b) (
+;;;     cond
+;;;     [(= b 0) a] ; Rekursionsanker
+;;;     [(= a 0) b]
+;;;     [(> a b) (
+;;;         euclid (- a b) b
+;;;     )]
+;;;     [else (euclid a (- b a))]
+;;; ))
+
+;;; (euclid 50 5)
+
+;;; (and #t #t)
+
+;(define (bar1 lst) (
+;    map foo (filter abc? lst)
+;))
+;
+;(bar1 (list (make-abc 1 (list 2)) (make-abc 3 4) 1231342154))
+;
+;(define (cartesian-prod list1 list2) (
+;    map
+;        (lambda (y) (map (lambda (x) (list y x)) list2))
+;        list1
+;))
+;
+;;(define (cartesian-prod list1 list2) (
+;;    cond
+;;    [(and (not (empty? list1)) (not (empty? list2)))
+;;        cons (list (first list1) (first list2))
+;;    ]
+;;    
+;;))
+;
+;(cartesian-prod (list 1 2)(list 3 4))
+
+;;;(define ( proof lst r g b ) (
+;;;    cond
+;;;    [(= 0 r g b) (map + (list 0 1) lst)]
+;;;    [(= 255 r g b) (map + (list 1 0) lst)]
+;;;    [else lst]
+;;;))
+;;;
+;;;(define (count-black-white img) (
+;;;    (count-black-white-of-list (image->color-list img))
+;;;))
+;;;
+;;;(define (count-black-white-of-list lst) (
+;;;    cond
+;;;    [(empty? lst) (list 0 0)]
+;;;   
+;;;))
+
+; TODO: use length of list
+;(define (count-black-white img) (
+;    list 
+;        (filter (lambda (x) (= 0 (color-red x) (color-green x) (color-blue x)))
+;            (image->color-list img)
+;        )
+;    ;( (image->color-list img))
+;))