@Dartinha Unfortunately, once Opera Sync data gets overwritten like this, there’s usually no way to restore the previous version from their servers. Opera Sync doesn’t keep multiple restore points or version history for recovery.
What you can try though is:
Log in on another device where you might still be signed in (sometimes old tabs/history are cached there)
Check if any browser profile/local backup still exists on your old Windows user folder
Contact Opera support, but realistically they’ll likely confirm it’s not recoverable after overwrite
For future, it’s a good idea to export bookmarks or keep a local backup alongside sync, especially for large history/tabs.