"Finished doing something"

Would you like to exmplain me why does it using "doing", please? And is it ok if I say "finished done something" instead? Thank you in advance

See a translation

This is a little complicated.

“Finished doing something” is a shortened version of “I have finished doing something”. Another way of saying that is “I have done something”. The word that comes after “have” is in past tense, which is why “finished” is in past tense. It doesn’t make sense to put two words in a row in past tense in this case, so “doing” is not “done”.

Really, “finished doing something” is more of a saying, that gets very complicated to explain why it is conjugated how it is. If you just remember that it’s “finished doing something”, you’ll be fine