Dear Sir,
I wish to offer you my help with developing your application on the Windows Phone 8 platform. I can promise you high quality results and you can expect high flexibility from me in order to suit your requirements. If you decide to award me this project, I would prefer that we have a bried audio/video call in which to settle on your requirements and needs. I also offer post-release bug fixing for a set period of time (we can negotiate that prior to the release).
I hope you will consider my offer. Best regards, Claudiu.