Facing a mental block starting a startup

This might be a lame post altogether but here I go. I have had an idea of a product / platform since about an year it targets primarily a category of small scale localised businesses(no not grocery stores but similar nontech domain where the tech is the enabler), what I have achieved (my background is 2year exp backend engineer) in the last year is a minimum viable backend of the same and a market fit survey with about 10 local businesses (who were interested) Now coming to block am facing right now is with business/legal formalities to actually make it official, don’t really know where to start looking for even guidance on “how to start” with those legal “stuff”. Another thing thats equally annoying is whoever I want to make this idea happen with always seems to interested and invested at start few days and eventually they fade out with no actual output of excuse of being busy, am not really what am doing wrong here. In my mind why I need a cofounder is to handle the frontend(this is what feel I need cofounder for). Any advise from anyone who are willing share some of their thoughts?