Where did the 50% of our beloved heroes go in the Infinity War MCU movie?

That green arrow and black canary costumes all depends on how the infinity gauntlet works, the idea is that it controls everything in existence so in theory thanos can decimate half the universe with the click of his fingers, however thanos himself doesn’t know that this would be the intended outcome, at the end of infinity war when thanos snaps his fingers the gauntlet breaks and burns his arm either implying he cannot use the gauntlet anymore or the power of the infinity stones was too much to bear for the gauntlet, this could mean that the end result is different to what thanos intended black canary costumes; either they are totally dead (literally turned to ashes) at the snap of thanos’ fingers, or they’re not dead completely and in a state of limbo (so their souls are trapped either by the soul stone or some alternate dimension), or the finger snap didn’t kill them but rather transferred them to some other plane of existence like an alternate universe or something else entirely happened to them. Maybe they were meant to be killed but some other force (for example the living tribunal) interfered and saved their souls. we’ll only know for sure in avengers 4 thea queen cosplay