請幫翻譯英文.不要網上翻譯

I would not know if I am buy it for you until next Monday because I need to wait for his response this Sunday.

我要下星期一，先知道可否買給你，因為要等待他星期日回應我
1. I need to wait next monday to know if I can buy it to you 'cause also I got to wait until sunday for him to give me a response.
2. Next monday I should know if I can buy it to you 'cause I got to wait until sunday when he will answer me.
3. Next monday I need to know if I can buy it to you 'cause it's necessary to wait until sunday when he gives me a reply.

As I need to wait his reply till Sunday, I can't tell you if I can help you to buy after next Monday.

I assumed買給你 meant to sell to someone? Maybe it's a typing error. Otherwise, the sentence doesn't make sense.

My versions are:

I won't know whether I can sell it to you or not until next Monday, becasue I have to wait for his answer/reply by Sunday.

I won't know whether I can sell it to you or not until next Monday, because he will give me an answer/a reply on Sunday.

Not until next Monday, I will not know whether (是否) I should buy for you. It is because I need to await (等待) his reply on Sunday.

P.S. After " await " , no need the preposition " for " .

I need to wait until next week to see if i can help u to buy it because i need to wait him to tell me on Sunday.