Gundogan is very good for tiki taka after about six years with Pep Guardiola at Manchester City. Even Pep upgraded initial tiki taka from Barcelona to Bayern Munich then Manchester City, the core idea of tiki taka was digested by Gundogan. He will not have difficulty in Barcelona especially we saw Xavi did not change the initial tiki taka too much in one season and a half with Barcelona.
Gundogan will have no trouble with Xavi's game tactics. he will be a tremendous support for Lewandowski. this season could be the most productive season for Barcelona I think. I don't understand why Pep could let Gundogan go to Barcelona. he is one of City's important players in getting a trophy this season. I'm sure it will be Xavi's luck this season.
I think Pep has his own reasons why Gundogan was allowed to go to Barcelona, I think Pep wants Gundogan to gain new experience at Barcelona and in the Spanish league, besides that Gundogan can also accompany Lewandowski at Barcelona, that will be a good strength this season, especially considering barcelona did not look good in UCL last season despite winning the league.
I also believe that Xavi will not waste this opportunity with the arrival of Gundogan, of course it will bring fresh air to get players who might be able to make Barcelona's attack power even sharper. at least barcelona can be better than last season. Gundogan is the player who managed to bring Manchester city to the Treble winner last season and of course he was very instrumental in many Manchester City matches, it was time for him to show his abilities in the Spanish league with Barcelona. I'm sure he'll adapt quickly too