how is damage delt with doublestrike

[rotom]

how exactly is damage dealt with double strike?

[DatAsh]

There is a First Strike damage step, where first strike damage is dealt, then the regular damage step, where regular combat damage is dealt.

[rotom]

if i kill the blocking creature in first step do i do damage to the player in 2nd step?

[Arix]

Not unless the attacking creature has trample. Once a creature has become blocked, it remains blocked all throughout that combat phase. It won't deal any damage to the player/planeswalker it's attacking, even if the blocker leaves combat.