Which of the following is the correct sentence to ask a person if he is okay to help me? (The help here is, asking doubts in another language.)
I will be needing your help, if it is okay with you.
I will be needing your help, if it is okay for you.
1) Is definitely most common in common usage. ‘Okay with’ most commonly confirms politely that the person is willing to/comfortable with helping.
‘Okay to’ might imply that there was some reason the other person might not be in a state where they are able to help, e.g. (To a sick person), “I will need your help if you are okay (well enough) to help”. ‘Okay for’ can be used to refer to something more specific, e.g. “I will need your help if (some date/time) is okay for you”.