After the Big Snap, the whole universe lost half of its creatures. Avengers shattered when everyone looks for the answer who’s going to save the universe. Nick Fury sends a message to Captain Marvel. Who’s Captain Marvel? what are her powers? Where is she? everything remains unknown. As per Captain Marvel trailer, Captain Marvel is a Pilot in Airforce might have hit in space and lost all her memories and reached some place their she gets some supernatural powers and joins good side of an Army. Again She returns to earth to search someone there she met Nick Fury and regains her memory.
Coming to Avengers Endgame Trailer begins with Tony Stark sending a message to his love Pepper saying that He’s running out of food and Oxygen and might die anytime. Tony is in a Space Craft which means after the Snap Tony and Nebula started from Titan in Spacecraft. They might be trying to reach Earth or some nearest place to get food and Oxygen. Where Tony and Nebula lands will be the breaking point of the movie and from there Tony finds some best Idea to defeat Thanos.
[Earth] Steve and Natasha in a discussion with Banner to proceed next level of execution. Their discussion ends in search to find Scott and Shuri. Surprisingly Scott reaches Avengers facility with his Van. Natasha meets Clint some part of China why Clint is in China with a new suit is a mystery. Overall this is not an actual trailer its just to maintain the Avengers heat with title release.