Make a custom template for landing page

Hello everyone, I'm very new here, I was doing my own research about running some good Landing Page that's load fast and I found Grav CMS,
I looking for the way to make a landing page with Grav, how hard is to implement all features on Grav?

How hard it to purchase some theme on ThemeForest.net and apply it to Grav?
Is there any freelance database who can do it?
my ideas it to have a good template that I can duplicate many times on different domains with the same template structure but different products.

Please give me some advice,
thanks!

Welcome @akus,
This work could be an hard stuff without developing expertise,
you can take a look here as a starting point, to get you a good idea

bless