I don't know because I haven't watched any of the tv spots. But if I thought in depth about it I'm sure I could. Besides you realize knowing the arcs of a movie isn't the only things that can get spoiled. Little interactions and details are important to a movie as well and I don't want to be spoiled on those either. So I don't know why y'all keep saying this at all in here.
My point is you know maybe 3 or 4 of the major plot details (typical if you watch the trailers for any movie)
We know Loki gives the cube/space stone to Thanos
Captain America, Black Widow, Vision, and Witch are fighting Proxima Midnight at one point
Thor and the GOTG are meeting up
IM, Spidey, GOTG, and Strange are gonna fight Thanos on Titan
Cap & co go to Wakanda
Cap, Panther, Widow, Hulk, Falcon, War Machine, Bucky, Wakanda, and IM fight Thanos' army in Wakanda (and actually it's been speculated/confirmed it's Banner in the Hulkbuster suit not Tony, which goes to show you how much we don't know)
You can't deduce much of a plot or arc from this stuff. You can "think about it in depth" as much as you want but at the end of the day you're still speculating and hypothesizing
Some details/interactions off the top of my head that will be major which they haven't shown yet: Hawkeye and Ant-Man's roles, Iron Spider legs, how Thanos collects the soul and reality stones, how Thanos is gonna get the mind stone, the fate of major characters who are bound to get killed, how Thanos takes care of the Asgardian ship, how Thor gets his new weapon, why Avengers have to go to Titan, why Avengers have to go to Wakanda, Hulk and Widow reunion, the actual way the movie ends, etc etc
Trust me when I say you're not being spoiled on shyt, just enough to get you erect without a nut bust