Thanks for the feeback!
We honestly didn't test the game enough getting carried away by our enthusiasm, and that the deadline was 2 hours away when we finally built the project for testing. I encountered a crash and found the reason, patched it then we both tested it by playing the game twice each from start to end, didn't experience any more crashes, so we assumed it was solved. Apparently it was not.
About hitting the enemies, there is a particle effect that plays only when you hit an enemy, a red spark burst thing, but I guess it wasn't as obvious.
Now we know for sure what we need to improve :)