project error on launch

im new to unreal engine. i followed a tutorial. in the tutorial i had to add a class (for the player charecter). then i got a small warning.
after opening the unreal editor i tried to open my project but it gave me an error and a fix button. after trying the fix button i got another error telling me to fix it manually.
how do i do that?
how can i fix this?

my project is called “Test1”

the following modules are missing or built with a different engine version

Would you like to rebuild them now?
[yes] [no]

second error:
Test1 could not be compiled. try rebuilding from source manually.

thanks alot,