"I have a trouble with would, could and should. Can you add it to your guide? (seriously)"
sure.
WOULD:
'would' is used to show a hypothetical situation; that is, something that can't or may not happen in the real world for whatever reason. for example, "if i were you, i would go to the doctor." i am not you, so i can't go to the doctor for you. i'm just making the suggestion.
SHOULD:
should is used for polite suggestions or predictions. for example, "it should rain soon." that means that someone predicted that it would rain today, and you're expecting it to do so. another example is "he should tell someone about that." that is, we're suggesting politely that he tell someone.
COULD:
could can mean hypothetical abilities, or the past tense of "can." example: "if i could jump a foot higher, i would be able to reach it." i can't really jump a foot higher, but if i were able to jump a foot higher, i would be able to reach it. another example: "i couldn't come last night." simply, i wasn't able to come last night.
from your name, i'm guessing you're french
if you have any trouble with "would, could or should," just remember: subjonctif. in english, there are no special verb endings like in french; instead, we use words like "would, could, and should" to express those hypothetical feelings towards actions.
"when it's done" means "we have no idea, we forgot to do that; we were hoping you would all forget we promised <insert exotic promise here>"