i’m not an expert but i did do this a few months back. you can’t run fsck on a mounted partition, and you only have 1, so the only way to do it is to take your SD card out of your pi and put it in another machine that can run fsck. the way i did this was put it in my laptop that was running linux, and follow a guide (something like https://www.maketecheasier.com/check-repair-filesystem-fsck-linux/ )

i guess you could also do on a mac also, via the command line.