Solving merge errors in Unreal

Hello! Me and some friends have recently started a project on the 2D template. We have a GitHub repository and have individual branches for each of us. There’s also the master and dev branches. We plan on merging our branches to the dev branch to test how everything works before merging it to the master branch. After a couple of weeks of work today we started merging our branches to the dev branch. However one of us ran into a problem. After I merged my branch to the dev branch he wasn’t able to do it as 2 files are causing conflicts. One of them is the .umap file and the other is our MainCharacter blueprint. I added some C++ code to it after reparenting it to an appropriate class and the friend who is having the problem added some blueprint logic to show a HUD and we can’t merge these two files now. How should we go around solving this without losing our work/not having the hussle to send files to each other to copy and paste work? And how do we avoid these kind of problems in the future?