Product testing for your friend cool. What do you think of tasty so far?
For me, I think its the best food order/delivery platform on the internet, over the years I have spent thousands on software that wasnt even close to this, and a lot of scripts dont actually do what they say on the tin.
As for theming my project, I am using a paid theme (html) and also adding my own touches, so its a combination of using ready made template and my own stamp on it.
There are a couple of ways to add a template, from admin area, you have to get familiar with child themes and templating /pages/partials/layouts or you could go straight to root file/folders and make changes.