Firefox should not delete anything unless you told it to?

If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again.

What about the rest of your profile? bookmarks, settings . . . .

Thanks but pls tel me what do you mean bu FredMcD said

Once the problem is fixed, perform the same repair on all computers/profiles before using sync again.

That depends on what the real problem was. Software updates, settings, bad programs . . . .