As per existing German Law for online transactions, the flow of checkout need to be like below. But we are unable to do so with your theme. Can you please guide us whether can we do like below-
1. When I click on "proceed to checkout button" in cart page, page of new user registration/existing user login/proceed to buy as guest options will appear.
2. After logging in I need be taken to Billing & Shipping address page. [click on next]
3. Then I need to be taken to Order review page. [click on next]
4. Then another page will appear where I can choose methods of payment. [click on next]
5. In this following page, user can see the product summary, payment details summary and choose to pay.
6. Once the payment is processed, the user should be redirected to Thank You page. Here we will express thanks to customer or user for buying the products from us.