@taufik.mukti That seems strange. Are you using the stable release or the snapshot release of Vivaldi? It might not work properly on the stable, I am using the snapshot.
@dLeon It's been a couple of years since I last used Opera for a period of time long enough to get a good idea of how well Turbo works, but I can say that Data Saver isn't as fast as I remember Turbo being. It would be really nice to have a data compression feature built-in to Vivaldi; I'm pretty sure I remember reading something about that being planned for the future. But I wouldn't imagine it would arrive before syncing, as Vivaldi still doesn't have the resources for those kinds of features.