I want to make an social network app bit like instagram with whatsapp.
file sharing, instant messaging profile etc.

did some research and found parse question is am i able to use a private database/server to store the registered users of this app?

I'm planning to hire a developer to create the app and have no experience with programming.

kind of a confusing question, but yeah. You store your users in a data base. And pull/push information to the data base as needed.

Yeah, you're going to want a database.
I would find a programmer that know a little a bit about system/server administration too, and then just not worry about these things yourself.