Cannot change disk permissions

Hello everybody

Ran into a problem:

After turning off the light, I noticed that I cannot change the files on the second disk, on the Internet it is written that the access rights must be changed, I looked and they really changed, when I try to change the access rights it says

chmod: change permissions for ‘file’: File system read-only

Help, what to do?

Unmount the filesystem and then perform filesystem check to fix errors.