This is an accepted solution.
Hi there @filip12!
Don here from Shopify.
It wouldn't be possible to change an existing theme into another one, but if you just want to transition your store to a paid theme you like I can show you how that works.
You can grab a free or paid theme from here in our theme store by clicking on 'Try Theme' on any individual theme there.
This will allow you to preview it for your own store, and even start to customise it, before you would need to pay for it.
Bear in mind that due to the digital nature of themes as products, all theme purchases are absolutely final and refunds can't be considered for these purchases.
That's okay though, as you'll be able to try it out and build it out for your store before you click to confirm if you want to purchase it.
You can have multiple themes saved to your store in the Online store > Themes menu, so that you'll be able to do the work of customising your new theme while your live storefront is still showing the built-out Debut theme in this case.
There's more info on how trying, buying, or adding themes works here on our help site that you can check out.
Check out the info shared above and ask me anything else you need to know!
Would you still be starting out with your store here?