how can i work with my friends in UE4 here is my discord for help
Use Source Control Management (SCM) systems like Plastic SCM, Perforce and Git. Depends which one do you like. But even I have widely used Perforce and Git, I prefer to use Plastic SCM for developers, Gluon SCM (Tool of plastic) for designers. If I would like to point out which one is good on terms of some fundemental topics at 0 - 5.
Also git is fully offline, you only need online to sync with server (which technically is remote copy of your repository), alone you can use it as a backup system, thats why it is recommended to use repository even if you work alone.
Plastic SCM also same thing, but you need to configure it properly. In Git side, its much more easy to have offline rep.