He wants another challenge so a move to Barcelona at least makes Gundogan happy to be there even though the Man City club can ensure they will win again but the choice of another team by Gundogan is Barcelona not Man City anymore.
Yes Pep Guardiola does not want a bad atmosphere because he does not want to let go of players if it is their intention to leave Man City never blocks so hard even with a suitable offer the player is always released.
For me Man City by losing Gundogan and Mahrez will not weaken their attack, Man City players can always create opportunities for goals.
Important layers departing the club this summer, ofcourse it won't affect their performance, because the club have growned to played without depending on a particular individual, they play together as a team. The club keep making improvements in every season, without hesitations. Pep Guardiola have no intentions of leaving Etihad Stadium this summer, it's very interesting how he managed to tighten the club and improved their performance over the past years. Presently, Manchester City is seen an elite club with good quality players.