Scared of Competition/Theft

So like you read in the title, I have this really good startup idea, however I need help from software developers, investors, etc. The only thing practically holding me back is that I keep overthinking what if someone screws me up, or the idea gets stolen, or … and I’m stuck in this loop.

To be more specific, I need to build a website, however I am not entirely good at that, so I currently need help from someone who is. So should I just trust them and assume the best, or should I make them sign something, or how should I approach this?

I’d appreciate any help since I’m young and this is my first real startup venture.