The reason Gundo is playing all the time is he is our only fit out and out central midfield player. He's not a winger and he's not a 10. Nunes is probably a CM player but not in the style of a Pep team. Foden increasingly looking like a 10. Lewis, god knows.
Grealish for me should get a go here. I've never been convinced he's a winger, although he helped us playing as a wide control player.
So the question is who plays in the three.
I think the front 3 should be
Foden Haaland Doku
Which means midfield is
Gundo
Bernardo. Grealish