Sorry I've been pelting you with my linguistic questions lately, but since I'm trying to do my best to make my English perfect, I just have to keep bothering you :)
Today's question regards something, I believe I could most adequatly refer to as the sequence of tenses. Without further ado:
While it's clear to me that when I use two separate verbs in one sentence, within the boundaries of one tense, the correct phrase should look like this:
I will go there and look for him.
I have been there and seen some serious shit.
I had broken the law and gotten shot three times, before I understood my mistakes.
And so on, random gibberish; these all are still correct, right?
Though somehow I became hesitant about whether a little more complicated sentence that I formulated would still be correct:
They are believed to have been there but not done a thing.
Something sounds a bit off for me here, but I'm not sure how I could fix it. "But not do a thing" isn't the right answer, I suppose, as it would clearly violate the verb tense consistency. Or perhaps I'm just overreacting and it's all okay?
Also, I would be highly grateful if you could point out my mistakes in any of my posts, should some inconsistencies occur.
Edit: Thank you so far, yet my doubts haven't been resolved completely yet :) I get that my sentences are correct, but would the last one still be if I were to say "but not have done a thing"? And if so, which one would you prefer, and would the latter case affect somehow the overall meaning?