This is Elias from Shopify Support. I'd be happy to lend a hand with this!
I understand you're using the Debutify theme and you're finding that the theme is too slow. It's important to note that Debutify is a third party theme and isn't available through our Theme Store, so it's difficult for us to say which theme is faster or better. However, since you can install up to 20 themes on your storer, I'd recommend trying out a couple of our free themes. This way, you can try different themes and use the same tests to decide which one you prefer.
That being said, the performance speed of a store can also be attributed by the apps you have installed as well. By removing any apps that you're not using, you can also optimize your store's performance.
I'd be happy to make some theme suggestions as well - are there any specific features you're looking for in a theme?