thanks a lot for your reply. Neither of those did the trick I am afraid. Windows firewall was already properly configured and shutting down Malwarebytes resulted in a really strange situation, MsMpEng working in the background like mad. Anyway as in most of Windows related cases a forced reboot seems to have solved the issue as after quite a while Dropbox finally managed to connect and sync so problem solved
By the way the green ticks on files and folders as well as all the other flag statuses have vanished a while ago but since the app is working and most importantly syncing it's not a big deal
Thanks again for your help, greetings from Greece!
Re: Dropbox Windows desktop app stuck at starting after the latest update