Muhammad,
Do you really mean that you have already done some work without even agreeing your fee!!??

This is commercial suicide!

You really MUST get your Contract (or whatever it's called in your territory) agreed before you start work!

As well as fees, this must define the rights, responsibilities and limits of liability for both parties.
This is a Legal Document, and you should seek professional advice from someone experienced with this type of agreement in your territory.

If you say where you are, someone may be able to suggest relevant local organisations which could help.