The info of the possible time travel kickstarts Captain Americas optimism, Black Widow's fighting spirit and Tony's desire to protect the earth, albeit a bit late with Tony. At the same time we see the characters who just haven't finished their story yet in a less strong change situation. Thor is so exhausted that only beer can convince him to take part. Well, not really, but he uses beer as an excuse. Hulk is just there because he doesn't seem to have much else to do except making selfies with fans. The rest of the team is also there, collected.
I've hardly addressed the time travel topic yet, because I've noticed that there are some logical gaps for many. I can only tell you so much about that at this point that it makes absolute sense. Everything is explained logically in the film and you just have to forget the conventional views of time travel in films, as it is said in Endgame. I'll try to explain this to you later. It's still too early for that, because I want to continue with the story scanning and in the end it fits more because the twist with the older Captain America fits very well, and why all this is absolutely logical and has no gaps.
The plan at the end of the remaining heroes is to travel to the past and get the stones there and put them into their own timeline. Who else as Tony Stark should solve this mystery of time travel? Yes, but he refuses until he is convinced by his own ego and of course by Pepper that he had to help all those who didn't have a great turn in the last years, as he did now with his family and his daughter.
So they travel back and from here on the absolute fan service in the movie also starts. Here are scenes that fire up the dreams of the older MCU fans, which are part of the MCU from the beginning on, because the film take up old events of this film series from a different angle. Be it a Hail Hydra saying Captain America in the relatively identical replica of the elevator scene from Winter Soldier. Ant-Man and Tony comment on Cap's first very tight outfit or the stair-hating Hulk, which we hardly really noticed outside of a fight at that time. Cap versus Cap is also an ingenious scene in which Steve Rogers with his heroism gets on his nerves or the curse of Loki with the dropped Tesaract, which obviously never happened in the main timeline. At the same time we get to know how wise the Ancient One, the monk and mentor of Doctor Strange, really was and what she knew about the future and that she did her part in defending New York in the first Avengers movie, even if in secret.
At the same time Thor gets one last meeting with his mother who died in the main timeline and he is just an absolute wreck. We see how broken this man is and he only gets hope through his mother's encouragement and his old hammer Mjolnir. Because Thor is still worthy, despite everything that happened to him, that's what the hammer shows him. His mother also says exactly what many fans who criticize this version may have overheard. Thor was never himself. We only saw in the movies how he fulfilled the expectations of others. To be a good king, to rule Asgard, to save the worlds, to be a good Avenger and everything else that goes with it, just a hero. But he never realized who he really is, what he is and what he can do. He has only recently realized what his real powers are, although he has run 1500 years with a hammer through the worlds. Thor's self-discovery phase is not over yet, no it is just at the beginning.
Part 4 
Part 6 
