Thanks for your answer!
1. Add to cart button stays in every product page.
2. I wasn’t specific about this, actually checkout page remains where it is but instead of direct payment or paypal as the next step it outputs simple form with listed ordered products as well as delivery info and sends it to email.
And is it possible to customize css, layout, add new elements for example additional product properties to woocommerce pages?
As I researched Woocommerce isn’t customizable as I thought. Maybe I am wrong?