Can you conquer multiple times if enemy gain control of Battlefield?

No. Once you've conquered (scored) a battlefield this turn, you cannot conquer it again — even if the opponent takes control of it and you take it back.

Per Rule 464.1, Conquering requires gaining control of a battlefield you did not yet Score this turn. And Rule 465 limits each player to scoring each battlefield only once per turn, by either method (Conquer or Hold). When you later regain control after the opponent took it, you are simply taking control — you don't score again, so it's not a conquer and won't trigger conquer abilities.

Your opponent can score it when they take it (since they're a different player who hasn't scored it yet — FAQ 244), but your reclaim is just a control change, not a second conquer.