Asking about my email content

Hi I am James.
I am working in my current company, but recently got a offer from other company, and they need me to start ASAP (less than a month). I have submitted my resignation letter today and contacted my manager about this issue. The problem now is he need to discuss with hr department before he could promise me. So I am going to send them an email below:
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Hi Sari Manager,

First of all, thank you very much for your offer to be an IT Manager in Exos. I am very happy to become a part of the company and work for the development with my complete knowledge and skills.

Regarding to the first day of my work on 17-07-2016, I have discussed with my manager about this issue, I afraid that I cannot make it due to our company policy stated that one month working period are required after the submission of resignation letter. If not, one month salary is require to repay. However, he is trying to discuss with hr department to check any exception for my case. I only can come back to you after I got any feedback from my manager. Hope that you could understand.

Best regards,
James

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I try to say in a very polite way, because the both job are very important for me, although new employer is my dream company, I don't want to spoil my name as well in my company. So could you help me improve my email and grammar correction. Thank you so much, my mother tongue langue is Spanish, my English is not that good.