(informal) in no time, in two shakes, in a flash, in a jiffy

(informal) to be all thumbs, to be very clumsy

it's one of those two things; there are two possibilities, there are two possible scenarios; you have two options; you choose(: either ... or)

(informal) not ... at all, not ... in the least

all things come in threes, things always come in threes; bad things come in threes / all things come in threes, things always come in threes; good things come in threes

(figuratively) to have a foot in both camps, to run with the hare and hunt with the hounds, to be sitting on the fence

doubly, so as to make sure, so that there be absolutely no doubt / absolutely! with pleasure! yes please!

(figuratively) to sign something enthusiastically, to jump at an opportunity, to grab an opportunity with both hands

(engineering) two-stroke engine

to kill two birds with one stone