CS0111 and CS0102 are pretty self-explanatory. You likely have a duplicate of one or more of your classes, which are now conflicting with each other.
Looking at your screenshot, “LevemItem.cs” next to “LevelItem.cs” is a bit suspicious. I’d start there.
In VS Code you can also press Ctrl+Shift+F to search all files, and look for “class LevelItem” (for example) to locate other files containing that class definition.
The “LevemItem.cs” and “LevelItem.cs” are different scripts and have different classes as well. Theese files are in my project since I started working on my game and I’ve never had any conflict before. I was working on the problem and I deleted the “android” folder because godot started giving me another errors. I did it just to see what could happen and it solved the problem (???). Well, I don’t know how can android folder be related to theese errors, but the fact that c# is experimental explains a lot.