"He ran and went up."
我想，這兩句子的差別是這樣: 如果你說"他跑了上去"，這個意思應該是他跑了，然後上去了，可是他跑上去了意味著他跑著上去了. 我也以為是跑上去了. 我有可能錯過了，但是我覺得這兩句子的差別應該是這樣.
What exactly is the context of the English translation? Like, he ran (ahead of us) and went up (the stairs)?
It's actually more like he ran up (something). 1: Where did he go? 2: (pointing to stairs) He ran up.
Its actually means: 他跑了 emphasize that "he ran" as an action to reach "up".
You are partially right about "ahead of us" because the speaker should be standing before "he" who ran up to say like this. But it's not always accurate to think that this sentence imply the person is ahead of him. It simply say that "he" use run, not walk or climb, as an action to reach the "up"