A bit confused about the player positioning in doubles. Say a player serves, after his game, can he also return the serve or does he have to move to the Ad court?
In doubles, just as in singles, the team serving alternates after each game. So, after a doubles player finishes their service game, they will then be on the team that is returning or receiving serve during the next game.
The two players on the team returning serve must begin each point on the same side ("their side" will be either the deuce court or ad court side) for the entire service game. Therefore, each player on a doubles team will alternate receiving the serve, or you could say each player returns serve every other point.
A doubles team may choose to switch which player is on the deuce court or ad court side after each set but cannot change in the middle of a set.