If you can build the backend, then you wouldn't have much trouble getting familiar with basic ios and android development. So, really, just start. Build one fea

If you can build the backend, then you wouldn't have much trouble getting familiar with basic ios and android development. So, really, just start. Build one feature and iterate. There's so much about your app that you don't know yet, and you will discover more and more with each step. Your problem is not the lack of a potential cofounder, that may come in time. Your problem is in thinking that you need a cofounder to build the first iteration of a mobile application. With all due respect, you're asking the wrong question(s).