Dear, Sir. Nice to meet you.
Thank you for taking the time to read my proposal.
I read your project description carefully and am very interested in working for your project.
I have already built many apps for 5 years and uploaded many apps on the app store, so I have rich experience in mobile app development as well as social networking development.
That's why I write quality apps for you, then I can satisfy your requirements fully and can offer good service until you satisfy with my work.
As an expert, I have great experience in app development so I can satisfy you and will provide full service until you satisfy with my work.
I'd be more than happy to offer my service for you and am so excited to hear from you.
Thanks and best regards.