Endgame 2.1 They went to different timeline to bring infinity Stones.

Since from part 1, we learned that Ironman secretly made well performing time machine ,he came to visit others at Hulk Labs and he brings Captain America sheild with him which he had take From him during Civil War fight. Then , start time machine and went to collect infinity stones. They split into diff groups to take those Stone.

Captain America , Ant-Man , Ironman and Hulk goes to 2021 timeline in New York . Then there were 3 Stones. 
1) Mind Stone : 2012 Captain America finds latest Captain and they fight each other but latest one after some final wins and take sceptor with him The sceptor had mind stones.
2)Time stone : Hulk went to Sanctum at Newyork to bring Time stone. During that time ,the stone was with Ancient one and doctor strange wasn't full teached yet. Ancient One denies that it will create multiple timeline but when he says because of some reason doctor strange i future will give a time stone to big villian Thanos . Then she is ok to give a Hulk stones and they promised to bring stones back in theirs own timeline.
3) Space stone : Ant-Man and Ironman went to take Tesseract from Avengers towers but because of Hulk 2012 which was made to take stairs spoiled and Tesseract fells before Loki and Loki went to different Places with Tesseract . At This point they failed to take Stones. Now captain America and Ironman decided to go back further in time at 1970 at United States Army's labs Where he met his father. And captain America manage to gather pimp particles and Ironman manage to take Tesseract from there.