Include Path Missing

I had a project in UE5 and when i added a new c++ class, the code i wrote, worked fine. I saved the whole lot and closed i down, but upon reopening the project the code was gone! I then went to VS code, to see if the problem laid there, the Code was all there, as when i last had worked with it and the same error messages (the update include path ones) were also there, as it was to begin with.

I went back in to Unreal, but could’t open it and got this, that said i should try to rebuild from source manually. i can´t seem to figure out how to rebuild from source or how to update the include path (or where to find it, if that need be).

i’ve been banging my head against the wall for far to long with this and would really appreciate, if anyone knows, what is up with all of it.