Hey
Hope you are doing well!!
I am up for this job and would be happy to assist you for a long term as I carry 3 years of Xamarin based app development experience. I have gone through the list of issues you shared in the job description and can fix them for sure. I am also having good experience working with HTML5, CSS3, writing endpoints, REST, SOAP, PARSE, JSON etc.
I can also show sample codes, backend of the applications if required.
Kindly get in touch with me so that we can discuss this further and proceed further.
Look forward to hearing soon from you.
Regards!!