Gatsu it seems like you are stuck in a partial update. It's a tricky situation.
Assuming you have a backup, you could try to delete composer.lock and vendor, then run composer install. This should fix the partial update state, but will cause some extensions to update.
Once that's done, check on which Flarum version you ended up. If you are still on the older Flarum, repeat the official update steps from there.
