Hello. I will be grateful for some grammar help.

Question

1)Which tense is correct in the context:
"they will get the documents ready by Friday" or "they will have got the documents ready by Friday"? Are both structures possible?
2)Is it possible to use "after" in the structure: "They have achieved much after the war / after the war ended" or is it only "since"?
3)Does the sentence seem natural: "She had been working hard for six hours, after which she decided to have some rest"? Do you think it's possible to use "after what" instead of "after which"?
4)Do you think it's possible (and natural) to use two present perfect tenses in the sentence: "they have been protesting for several days when he has finally accepted their demands"? I guess it's supposed to be in the past: "had been protesting; accepted", but is the present possible?
5)A similar question. "He has said he has been waiting for hours" (are two present perfect tenses OK here? I think it sounds better than the previous sentence.)
Thank you very much for your time and help.

Answer 1

1) Both are correct, except the second should be "will have gotten."

2) They achieved much after the war.
or
They have achieved much since the war.

3) is awkward. Better: After she had been working hard for six hours, she decided to take some rest.

4) Your first sentence is incorrect.

. . . had been protesting . . . when he finally accepted . . .

5) That sentence is fine. :-)