as_pavargau

I am trying to create an e-shop for a lithuanian audience and squarespace doesn't support this language as a language of your site. At the moment I can't find any ways to solve a problem that I ran into - I want to get better/full customization over my checkout page but all information I managed to gather is that there is no way to paste your own code in order to customize the checkout page(and make it lithuanian) and the customization options that squarespace provide us with are extremely limited. Also is there an easy way to change the words like "Quantity" over at the product page or "Login" in the header. If you have any solutions to my problem I would appreciate it.