Is there a way of customising downloaded themes? Shopify!

I have imported a theme from Envato Elements and are looking to do the following:

Remove and add section on home page
Create templates for pages where I can add sections
Remove the basket icon

Are any of these possible on imported themes? This is the first time I am using a theme taken from outside of Shopify so I am unaware of how customisable they are.

TIA.

All doable assuming you know how to write code or you hire someone who can - it’s unlikely to be possible without understanding the technical process