When I add to cart a product, I always redurects to login page even when I am logged in already

When I add to cart a product and when already logged in in my account then also shopware redirects me to login page instead of „Payment & shipping“ of step 2. My shopware version is 5.4.6. Can anyone explain me why I can’t place an order?

Since this is no general issue of shopware, you need to provide more information on the workflow, your installation itself (server setup) and the customisations of the shop. This might be caused by a wrong session handling of your server, but without a lot more investigation on your side, we can only guess.