I'd run your store URL through the Shopify Analyzer, it's a free tool our team built for the Shopify community. It'll help to identify any optimization opportunities and provide references on how to resolve them.
Also, please keep in mind that your Google Page Speed Insights/Lighthouse scores are a combination of various metrics, not just site speed. Your website could actually be performing very well, but still have a low score. We have an article that goes into more detail: The Truth About Google PageSpeed Insights for Shopify.
3rd party apps also play a big factor in your score since it's typical that if you have many apps installed, your score will likely be lower. This is why we recommend only installing apps that are absolutely essential and uninstalling anything else. It's worth noting that just because you uninstall an app doesn't mean the app's code gets removed from your theme. It's best to go through your theme code after uninstalling an app to ensure no leftover code exists.
I hope this info was helpful! If you need any assistance with optimizations, please feel free to reach out to our team at speedboostr.com/contact.