difference between can, could, be able to, could have, and manage

can - (чадах)
could - (чадсан --- ердийн зүйл, болон хийж чаддаг зүйл )
be able to - (чадах...)
manage - (дөнгөх, дийлэх...)
could have - (чадах байсан юм...)

Grammar: can  could  be able to  manageCan is used to say that somebody knows how to do something: Can you play the piano? It is also used with verbs of seeing, noticing, etc: I can hear someone calling, and with passive infinitives: The DVD can be found online.
Can or be able to are used to say that something is possible or that somebody has the opportunity to do something: Can you/Are you able to come on Saturday?You use be able to to form the future and perfect tenses and the infinitive: You’ll be able to get a taxi outside the station. I haven’t been able to get much work done today. She’d love to be able to play the piano.Could is used to talk about what someone was generally able to do in the past: Our daughter could walk when she was nine months old.You use was/were able to or manage (but not could) when you are saying that something was possible on a particular occasion in the past: I was able to/managed to find some useful books in the library. I could find some useful books in the library.Manage is more formal and less frequent than be able to. In negative sentences, could not can also be used: We weren’t able to/didn’t manage to/couldn’t get there in time.Could is also used with this meaning with verbs of seeing, noticing, understanding, etc.: I could see there was something wrong.Could have is used when you are saying that it was possible for somebody to do something in the past but they did not try: I could have won the game but decided to let him win instead.