Okay I guess the part of
if steps % print_every == 0:

is the problem.
As my test dataset contains 22222 “classses”(22222 signs) I would need 22222  as out_feature. Since this has nothing to do with my problem I will delete it and figure out some evaluation process and then share my solution here again.
As I simply copied this from the website I didn’t think of its purpose. I guess the best solution to this problem would be if I generate some more images of those 225 unknown images and test the accuracy of this neural net with them so the labels are fitting.