This card says "capture the top card of your opponents deck if able" does that mean you simply capture the top card until the objective is destroyed or until he runs out of cards in his deck?

If the objective is destroyed all captured cards go to the owners hand.

You can only use the reaction once per turn. So capture one card a turn. Would take quite a while to deck someone at that rate.

Note that using the Reaction to capture on each of your turns is optional. You may find it a good idea to not capture too many cards so that your opponent doesn't get a ton of extra cards when they do destroy the objective.

Ok thanks. You can capture anything right? Unit, enchantment, event card?

And if you have 2 tattooing crashes do you capture two cards or is the effect only happen once?

Ok thanks. You can capture anything right? Unit, enchantment, event card?

And if you have 2 tattooing crashes do you capture two cards or is the effect only happen once?

The Tatooine Crash allows you to capture whatever card is on the top of your opponent's deck, it does not matter if it is a Unit, Enhancement, Event or even Fate card.

If you have 2 copies of this objective in play, you can use each objective's reaction.

And if you have 2 tattooing crashes do you capture two cards or is the effect only happen once?

GroggyGolem has it right, you get 2 total captures. Each effect triggers independently, and each one triggers once. So while you do capture 2 cards total that way, it is one at each objective, you can't stack both captured cards on the same copy of Tatooine Crash.