Vincent Kompany still has no experience in the Champion competition so he cannot improve the mentality of Bayern players but many people should understand what happened because last season was the first season for Vincent Kompany and he has succeeded in lifting Bayern Munich's performance even though they have not succeeded in the Champion League competition but for next season Vincent Kompany with Bayern Munich is worth considering.
I do not agree that kompany is completely inexperienced in the champions league, last season he coached Bayern Munich to the champions league, they did not perform so well but it was not completely a bad experience, he actually used last seasons champions league to gain the experience he has never had, so this season he will not be playing as a completely inexperienced team, and on the Champions League it is almost normal for a first time coach to not do so well but from his second time which is next season we expect a better experience than last season.
Maybe what @Fakhrulenclix meant was that Kompany has no experience of winning the Champions League title. It makes sense that anyone might doubt the Bayern Munich coach.
Kompany was able to bring the club to the quarter finals last season but the results were not very good. If you look at Bayern Munich's performance in every match you will know that the players' mentality is not too great and was successfully eliminated by Inter Milan.
Except for last season when Munich managed to reach the semi-finals, I admit that Kompany has given a good improvement to the club.