looking for a template know-how

Hi everyone!

Im looking for a template or a way of having one landing page which anyone can see and fill in a form, and a website in a sub domain of folder where only registered people can see what has bee submitted and choose request and clear them.

Hope this makes sense, Its bit like people submitting jobs and builder contacting them with offers. That’s the kind of thing I am after

Additional info: only registered users from another website can log in. nobody but those registered users should know that URL to this website that I want to create. So the actual website could be a admin looking interface like Amazon seller account or ebay.