Writing documentation or getting users

My partner and I made teen social app and now we have our disagreements about next steps. I say we should focus on getting users and he says we should focus on documentation so we can pitch to investors. It's important to say that we live in different countries and even if we get some money it's hard for each of us to relocate just like that.

So we made social app, there are ton of social apps out there. From my POV writing documentation and preparing pitch for investors is worthless and time consuming at this point. Answering some common asked questions like:

How do/will we make money?
What is your (our) cost structure?
Who are your target customers?
What is the financial size of your market?
Who are your competitors?
What is your competitive advantage?
What is your path to customers

won't get us too far. Since this is social app it's really hard to put some realistic numbers there that will prove investors to invest in us since he/she can invest in any other social app claiming the same.

From my perspective we should start getting users and get some traction and let real numbers do the talking.

What is your opinion?