Please show me example sentences with is this grammar correct? "if i could do, i would have done it long ago?" . Tell me as many daily expressions as possible.

See a translation

- in response to a question “why not do it?” , your answer is grammatically correct without the ‘do’. Therefore: “if I could, I would have...”

- in response to something like “ let’s go! Do it!” , your answer would need ‘it’ after ‘do’. Therefore: “if I could do it, I would have done it long ago.”

Extra Examples:
#1 : “cmon, just jump”
Response: “ if I could jump, I would have done it.”

#2: “why aren’t you coming to France with us?”
Response: “ I can’t go. if I could go, I would have done it long ago.”

I hope this helps.