I got what it was... Stupid win10 had set me up for GMT -8 and I was at GMT+2 so when I tried to sync, firefox just wrote over my previous settings... WHY on earth would you take in account the users time settings? Because of this silly mistake, and i`m sure no one will care enough to help me and get some kind of data back, I as a web developer am stuck without any of my bookmarks, passwords and so on. Ya.. thanks.

Wow, I never heard of that happening before. Different UTC offsets ...

Usually when Sync is used (improperly) as a backup medium when reinstalling an operating system or installing a new operating system, we figure out that the user requested a new password for their Firefox Account, which automatically wipes the saved Sync data. The FxA / Sync password is used to create the dual encryption "keys" and when the password is changed the saved data is rendered useless; the "new keys" can't decrypt the "old data". Plus that process serves as a maintenance feature, to provide a means to clear corrupt data and "start over again" with a fresh load of data.

Unfortunately there isn't anything that Mozilla can do, there are no saved backups of data that is on the Sync server. And other than accessing Sync via a Firefox browser with the correct kA & kB encryption keys (a 26-character alpha/numeric "key" for each) there is no way to get into a users account to try to retrieve the data. But if the password was changed, there's no data there anyways.

Why would I want to change my pass :) This is what I did: I used sync on my old Windows I reinstalled the OS. I installed Firefox Dev edition and typed in my Acc and Pass. Waited a bit. When I opened history there was nothing. Get shocked. Install Firefox standard. Sync again. Get Tabs from current Firefox Dev edition. Start yelling :)