ktard already gave sos where Russo brothers explained all the biggest questions..

u guys still asking? move on la

He had to make another jump back to the main universe at the end to give the shield to Sam.

but the russo brothers' explanation cause a new plothole
if we follow the earlier rules, then he has to appear on the machine, but in the movie he shows up on a bench. they contradict their own rules 

This!

but i have no idea how cap returns to 2023 without the suit or through the portal.

It seems they don't need the portal to travel through time - demonstrated when they traveled to 1940 after they lost the tesseract to Loki

Once they mentioned time travel I immediately knew this was going to be a fanservice movie with throwbacks designed to elicit nostalgia.

Anyway one huge plot hole. I thought they said each avenger only had enough Pym particles for one return trip each. So how did nebula's Pym particle become enough to transport thanos entire freaking army over?

Here is where paying detailed attention pays off.

In 1970, when Captain America was stealing the Pym particles, he took 4 VIALS. Use 2 for him and Iron man to go back future. So that leaves 2 vials.

Evil nebula knows how it looks like and uses it to transport Thanos with army over.

Russo edy addressed this question. Ebony Maw was able to replicate the formula.
Turns out you only need grape juice, jello and sugar.

Lol I just read it. Their answer does seem sound too - now I know why Maw was featured quite prominently in Endgame compared to the other 3 Black Order members.

doesn't have to be a branch if it's like this:

shield was destroyed in the final battle, but shuri and t'challa were snapped back by banner, so it's much easier to repair/replace the vibranium shield. he then leaves the shield in the avengers facility

after returning the stones and mjolnir, he goes to be with peggy, but makes sure not to cause a change in the past, thus prevent a new timeline. grows old, then goes to the avengers facility again to pick up the shield and pass it to falcon

1. Him staying with peggy itself is a change. Remember peggy was supposed to be married.
2. How does he goes to the avengers facility without the portal?

this theory would demand the person she married (after cap was frozen) be the "future" cap that went back. after all they never really showed his face or revealed his name.

if she keeps the identity of her husband a secret from "past" cap, then "past" cap won't make any decision to cause a change/new timeline, then "future" cap can just grow old then just travel via normal means to the facility without the portal

but the russos say that's not what happened, so nevermind then 

this theory would demand the person she married (after cap was frozen) be the "future" cap that went back. after all they never really showed his face or revealed his name.

if she keeps the identity of her husband a secret from "past" cap, then "past" cap won't make any decision to cause a change/new timeline, then "future" cap can just grow old then just travel via normal means to the facility without the portal

but the russos say that's not what happened, so nevermind then 

Prime timeline Peggy married someone else..

Alternate timeline Peggy married Captain..

Prime Captain returned from Alternate timeline to Prime timeline after spending his life with Peggy..

i thought so too but then if cap already in an alternate timeline he can only travel in that timeline only.

but the russo brothers' explanation cause a new plothole
if we follow the earlier rules, then he has to appear on the machine, but in the movie he shows up on a bench. they contradict their own rules 

well..thts what the Russo bros said..

so is canon...

no matter how hard we try to explain the plot holes or inconsistencies..

whatever we say is still not true...

only what the directors said can be considered as true and canon..

sure but it just means they'd already going against the rules that they themselves established therefore it's inconsistent.  i would rather prefer that they'd retconned peggy's marriage and we got 2 steve coexist all this time.