Flick got a very good team, he doesn’t need to start over, put something together piece by piece to get a result, he already has a good team after Xavi, so it will be easier for him to start, but the final result will depend on the strategy he will use, and the decisions which he will take during the game. He also has experience managing large teams, so he can achieve good results, he has almost everything necessary for this. And if he holds out well in the first season, then he will be able to get the opportunity for new transfers.
Xavi leaves a lot of convenience for Hansi Flick in continuing and improving Barcelona performance next season, hansi Flick of course now has a team that is actually strong enough to compete next season, so Hansi Flick only needs to adapt his strategy and style of play to the Barcelona squad this time in my opinion, next season, I personally hope that Hansi Flick will try to focus more on the domestic league than the Champions League next season because in my opinion their squad is not capable.
Barcelona finances which are in a bad condition, will of course prevent Hansi Flick from building his squad, so it will be difficult for Hansi Flick to optimize their players to compete in La Liga and also the Champions Leagues imultaneously, so that's why it's better for Barcelona to focus on La Liga is in order to break Madrid dominance in the future, with the current financial situation of course we shouldn't expect any fantastic transfers from Barcelona in summer seasons.