I'd expect them to stay up comfortably, and having players all speaking the same language will be good for their squad, but like others have pointed out, there are a lot of good players in the premier league now.
Fulham, Brighton, West Ham and Huddersfield have all spent monumental amounts on players, so it is not that out of the ordinary for this summer.
The real test will come next season - do they push on from staying up, or do they then start to sell players like Neves to rivald if he thrives in the league?