I keep falling through a floor texture I've made, even though it didn't happen in the tutorial I watched. When I tried to fix that bug, the new map didn't load, even though I changed the name of the start location. Can anyone help? Also, how to you rotate the view in the level editor?
You rotate the view with Alt-M1. Alt-M2 zooms, and Alt-M3 pans. Scroll wheel also zooms.
There's a check box on planes which says "Collides". Make sure that is checked.
If map changes don't show, it might be caused by a cache file in your maps folder. Check and delete any .map_cache files you find.
If these are actual bugs, perhaps you should try reinstalling the game in case something messed it up.