If a creature has both lifelink and deathtouch does it deal deathtouch damage and gain life at the same time?

When a creature with both lifelink and deathtouch deals damage, that single instance of damage carries all the properties of both abilities at the same time. There is no conflict between them — they simply both apply to the same damage event.

Deathtouch means that any amount of damage the creature deals to another creature is considered lethal, destroying it (CR 702.2c, 704.5g). Lifelink means that whenever the creature deals damage, its controller gains that much life simultaneously with the damage being dealt (CR 702.15b). Neither ability cancels or interferes with the other.

It is important to note that lifelink does not use the stack — the life gain happens at the same time the damage is dealt, not as a separate triggered ability (CR 702.15b). Deathtouch similarly is checked as a state-based action after damage is marked (CR 704.5g).

Concrete example: You attack with a 2/2 creature that has both deathtouch and lifelink. It deals 2 combat damage to a 5/5 blocker. You immediately gain 2 life (lifelink), and the 5/5 is destroyed (deathtouch), even though 2 damage would not normally be lethal to a 5/5.

This combination is considered very powerful — even a 1/1 with both abilities can kill any creature it damages and still gain you life in the process.