On that screenshot’s error tab you can set the dropdown Build + Intellisense to only Build. Intellisense will show a lot of garbage even when there are no actual errors.
Now that you show more of the screen in that screenshot I also see that this file is not a header file but a .cpp file. cpp files do not use #pragma once, that is just for the .h files. You also don’t include .generated.h headers in the cpp file. See if fixing all that reduces the error count. You should also look up a tutorial on the web so you understand when and where to do things such as includes because this is very important, else you will run into many errors after a small mistake.