I may have deleted a GameMode that I do not use, but it prevent me from launching to my phone, any suggestions?

LogPlayLevel: Error: ERROR: System.ArgumentException: Attempt to construct staged filesystem reference from absolute path (/UI/MainMenu_GM.uasset). Staged paths are always relative to the staging root.

Your SD card or internal storage (depending on where you’re deploying the app package) might be running out of space. This thread discusses how to clean up the UE4Game folder which might be eating up a lot of storage space and causing this error.