Bernardo Silva and Kyle Walker deserve to be kept because of their performances, but I don't think Manchester City should ban Ilkay Gundogan and Riyad Mahrez from going to other teams. If possible, Pep should persuade both players to stay at least for next season, but if he has to choose one for one reason or another then I think Bernardo Silva is the most deserving.
Walker is the best defender Manchester City has and it is only right for Pep to be worried if he goes to another club in this transfer window. However, Bayern Munich continues to tease Manchester City into selling walkers in this summer's transfer window. If you look at Manchester City players, almost all of them have pretty good quality, so it's only natural that teams from other leagues will take advantage of the opportunity to tempt Manchester City players in this transfer window.
Several Epl teams have continued to put in quite impressive efforts in this transfer window one of which is Newcastle united. Seeing Howe getting a large budget to make changes in the body of the newcastle united team, it is possible that newcastle united will become a strong competitor next season in the top 4 big.