Thank you for your inquiry.
Yes, you can do this by going to configuration/payment methods in the navigation to your right. Afterwards, choose the desired payment method and change its name in the field called Title.
I hope that helps!
EDIT: Apparently it is not possible to change the payment method titles in shopify.
However you can force your checkout to be in a specific language.
In order to do this, you will have to access your shopify integration (in the navigation to your right: click on shopify on the bottom).
Afterwards click to "edit" the shopify integration you want to modify.
There should be an option called "Checkout Language " where you can set this to swedish.