Помогите кто знает английский!

If you have no time for answering me, then I can ask you later when you are free

Might I inquire while you are free?

If you are busy now, we can get in touch later. Let me know when you are free/have more time.

If you have no time to answer me, I can ask you later when you would be free

if you have no time to answer, I can ask later, when you'll be free

If you have no time to answer me, I can ask you a bit later, when you are free.

Правило:
В придаточных предложениях времени (when, as soon as, before, after, till, until) употребляем настоящее время, если в главном предложении
сказуемое выражено действием на будущее время или модальным глаголом.
Правило:
После придаточного предложения времени русское слово "ТО" не переводится,
т. е. then - не писать.

Британский вариант: If you haven't time to answer to me, then can i ask you later when you'll be free (you'll be not busy)?
Американский вариант: If you don't have time to answer to me, then can i ask you later when you'll be free (you'll be not busy)?

If you have` t got time to answer me, I can ask later, when you` ll be free

If you have no time to answer me then I can ask later, when he's free?