Hey Cryforce,
Do you happen to have the error from the crash reporter, or perhaps the machine ID from the error? Also, have you gone into your project file > saved > back up? If so, the .umap should be there. It’s best to practice making backups of all of your projects, especially when big changes are being placed into the scene. Within your saved file as well, there is a file which you should be able to gather any from that may be helpful.
Looking forward to hearing back from you, thank you. 