Marketplaces always a bit tricky because you have two separate audiences: The buyer side and the supply side. The benefits and motivations will be different for each side. So the first thing I would do is create separate pages for each. That way you can tailor your message.
I would focus on building up the supply side first. That doesn’t have anything to do with this landing page. It’s just a bit of general advice based on how other marketplaces have been built and grown. I read that Lyft paid drivers to sit in their cars when they launched to ensure that they had the supply to meet potential demand.
Your headline does a decent job of explaining what you do, but it’s lacking any sort of benefit or excitement. People don’t really care about what products or companies do. They care what products or companies do for them. Lead with the value you provide. (Again, this is easier to do by creating separate pages for the two sides of the marketplace.)
It’s good that you have the form above the fold, and I like that the button wording is a specific action. You could make it more effective, though by adding more context. Why should people join the community? What happens when they do? Perhaps you could add a line of text and maybe a header above the form. It wouldn’t hurt to make the form stand out a more more, too.
I’m not a fan of the background color. It kind of clashed with the first image, and it doesn’t offer great contrast with either the black or knock out white text. I would consider choosing a different treatment. You may want to have a few different backgrounds to visually separate the messaging areas. It may be helpful to consult with a designer or look for examples of templates and live pages you can mimic design-wise.
Hope that helps.