is this contract is legal according to Islam in which Time and Quantity is not fixed of the goods which I have to supply

According to our understanding of your question, a person ordered goods but the quantity and time for supplying the goods and payments is not fixed.

If our understanding is correct, then such a contract is invalid as the order and other related issues are not specified. That leads to a dispute. In principle, any transaction that has a potential of a dispute is invalid.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai