@Simone-Brunacci It’s frustrating to lose important research this way. Restoring from a disk backup on your external hard drive could indeed be a solution, as it may return your browser to its previous state with your open tabs. However, I’d recommend ensuring that the backup is from a time when Opera was functioning properly.
It’s also worth trying to check Opera’s history to recover some of your research, even if the tabs themselves weren’t saved. Additionally, some third-party extensions like 'Session Buddy' can help save and restore sessions in the future. I hope you find a solution soon, and good luck with the antivirus support! Keep us updated on how it goes.