Whenever I go into the locker room, there's just a black screen. The same happens when I try to peek in through the picture. When I went in I couldn't get out. Then I saved the game, quit, tried to go back into the save file, but it got stuck on a permanent loading screen. PLEASE HELP I CAN'T PLAY THE GAME AT ALL UNLESS IT GETS FIXED.

You might want to try posting this in the stickied Bug report post (https://itch.io/t/650889/bug-report) as it will probably get more attention.  It seems someone else has posted this issue in there already as well.  The developer says that a fix is coming soon, though I'm not sure whether that was posted before or after the 5.1 release.  If you're on 5.0 (not 5.1) you might try downloading the newer version, as it seems that there were two releases pretty close together.

Hello, This issue was fixed in V5.1