I think, Barcelona new manager will going to do perfectly well next season but Barcelona management need to invite some new potential players in this season so that they will not going to experience what they experienced from the beginning of the la Liga league tournament, that made them not to win the title. Robert Lewandowskii is getting older which many people can feel it from his performance, which the new manager need to look into it and bring in new young striker that can handle his position very well next season to bring glory to the name of the new manager next season. Base on the plan of Barcelona in this summer season, I think they will use it well to ensure they will be able to win champion league title and la Liga league title like what Real Madrid did this season, because Real Madrid prepared well to make it happened in reality to win two titles in a season.
I don't know what underlies you so confident that Hansi Flick will make a lot of changes to Barcelona next season?
Honestly, I personally doubt that this happened, maybe even Hansi Flick will not be able to make many changes like Xavi has done so far, Barcelona financial condition is of course the reason I doubt this, indeed so far Hansi Flick is a great coach and is able to give a lot of achievements to the team he has coached so far such as Bayern Munich, But let's not forget that when Bayern Munich won at the hands of Hansi Flick, at that time Bayern Munich had spent hundreds of millions of euros to build its squad, then this season will Barcelona be able to do what Bayern Munich used to do?
Barcelona certainly have a great striker with Lewandowski in the squad, but still they can't expect much from him given his age, Hansi Flick may be able to maximise Lewandowski abilities next season as a Barcelona striker because he doesn't have a better option than Lewandowski, Laporta has admitted that they struggle to bring in a great player to compete with Madrid and the only option What they have at the moment is to optimize academy players to help Barcelona compete in La Liga and the Champions League.