What to watch before you see Avengers: Endgame
https://www.cnet.com/news/what-to-watch-before-avengers-endgame-what-to-know-about-mcu/
See how much time you have below, note the important films, check their runtimes and then find out where to stream the MCU movies.
If you're only willing to devote Saturday or Sunday to a catch-up session (or you only have a day to get a friend up to speed), these are the absolutely must-see movies.