Tell me please, who can I contact for help on issues related to the development

Tell me please, who can I contact for help on issues related to the development of a mobile application for money transfers?

Have you tried searching on Google? You should seek help with a professional team and the easiest way to contact them is by searching through Google, there in the same results you will find hundreds and hundreds of these professional teams

Have you opened your own bank? Well, if your activity meets all the standards and rights to allow the use of money transfers, then you can contact the developers of such applications who will absolutely legally make such an application for you.