Disk Utility fails on first aid and I can't erase

Hi! I want to reformat my MacBook Pro. I started the process and got the black screen with the blinking question mark. I looked that up and it said to go to disk utility via command r. I did this and see that the Macintosh hd drive fails first aid. When I go to erase APFS in drop down is grayed out and erase is grayed out. I can select something other than APFS, but I really don't totally know what I'm doing. What should I do? Thanks!