Hello Sir,
Hope you are doing well!!!!
I can full fill your requirement easily because i can play very well with code which is developed by other developer. I can update your code without affecting your old functionality.
Secondly, I can start it by today itself just after your confirmation.
I'm having 7+ years of experience on Android and developed around 70+ applications which is almost on Play Store.
I am also looking for long term collaboration.
Lets have a quick discussion fore more info.
Thanks & Regards
Dharmbir Singh