Please share your store URL and Screenshot.
So that I will check and let you know the exact solution here.
Please provide website url and if your store is password protected then also provide password So I will check and provide a solution here.
Nick here from Shopify. Great question!
I asked our theme support team if this was possible and they mentioned we are unable to make edits to the dynamic checkout button because it’s branded. Paypal use rectangular buttons and it’s important to match the familiar style, both because Paypal want it that way and to maintain customer trust.
In saying that though, if you still really want to make the change, your best bet is to hire a Shopify Expert to do it as it would involve some customisations. You can see the Shopify Expert directory from the link here to research and find one you resonate with for this.