Gvardiol might indeed be a great player and there's no doubt he can strengthen Man City and suit Man City's game. but other names like Raphael Gurreiro are equally great players. In fact, he can always play his role well when he is played at the back or in the midfield. and to replace Gundogan who is said to be leaving Man City, the suitable player to replace him I think is Kovacic. Kovacic also seems to have agreed to sign for Man City and that means he will leave Chelsea. And I think Chelsea should be able to keep a great player like Kovacic more. But maybe Kovacic himself is not interested in staying longer at Chelsea.
Manchester City already has many center back players, I think Manchester City want to sign Gvardiol is for long term investment since he's still 21 years old.
Both of Guerreiro and Tierney are left back players, there's no pure left back in Manchester City, that's why they want to sign 2 players. Usually Ake or Akanji playing in this position, if Pep already get a good left back players, I think Manchester City will not extend Akanji contract.
Kovacic, a good midfielder who has a good dribble skill and ball control.