How did Dr. Strange bring everyone back to the Avengers HQ without him possessing the stone? The stone is supposedly in the gauntlet. So how did he do it? I haven't watched the Dr. Strange movie so maybe I'm missing out. Can he do that without the stone? Did he train for it? I watched the majority of the MCU movies but I'm still really confused.
As some people already said, Dr. Strange didn't bring anybody "back". He just created the portals so that other characters could arrive to battle easily (these characters got alive again when Hulk used the stones).
Wong can also create portals, and he doesn't have the time stone (for instance, he creates the portal that cuts the hand from Cull Obsidian, one of Thanos' children, back in Infinity War.