So,

Distant Strike

At 11th level, you gain the ability to pass between the planes in the blink of an eye. When you take the Attack action, you can teleport up to 10 feet before each attack to an unoccupied space you can see.

If you attack at least two different creatures with the action, you can make one additional attack with it against a third creature.

My question is usually ranger will have 2 attacks, so will I be able to teleport 20 ft.? Also if I play TWF will it be 30ft. worth of teleporting or is it still 20ft.? Also what if we throw Haste in the mix?

Distant Strike only allows for teleports when you're attacking using the attack action. (2 from extre attack, and maybe a 3rd if these attacks hit different targets)

Haste grants an additional attack action (with a maximum of 1 attack), which would allow an additional teleport.

TWF on the other hand uses your bonus action for the additional attack, so Distant Strike has no effect.

as I read it, with extra attack you could teleport 10 feet, then 1st attack, teleport 10 feet, 2nd attack, and if you attacked two different creatures then you get the third attack on a third creature, allowing to teleport 10 feet before the third attack so potentially 30 ft.