customize checkout

[Roeiam]

 

i am trying to chagne the checkout page text and i didnt mangae to do it
i edit default theme content but it didnt change

also i have another requstet i want to remove the sale line and replce it with costumize code 
i want it to be
כולל ₪40 תשלום מע"מ
and the 40 is a Formula of the price X 0.17
(This is for tax calculation and is equal to 17% of the purchase price)