test_string = "Denne strengen skal reverseres"

def reverser(string):
    test_list = list(string)
    counter = len(test_list)

    reverse = ""
    while counter != 0:
        reverse += test_list[counter-1]
        counter -= 1
    return reverse

assert reverser(test_string) == "seresrever laks negnerts enneD"
assert reverser("Denne") == "enneD"

print(reverser(test_string))