Thank you for using the Shella Shopify theme.
The page speed depends on content, features and apps.
Each new app adds JS and CSS. Loaded from new server. DNS lookup, connect to new server all these slowdowns page load. Choose only needed apps. It's up to you what is more important for your store, additional features or some more points for page speed. (I believe features is more important)
Each new element on the page slow down page speed. For example we disable product options on home page to get higher speed points.
Give me your store URL, to get more details what resources slow down the page.