Germany has a very restricted shopping hour. In fact, all German speaking countries have a limited shopping hour. Do not go shopping on Sundays because in Germany Sunday is for relaxation. It is not intended for shopping. The same thing goes for holidays. The best time to shop in Germany is during weekdays from 8AM to 9PM. Only gas stations are open after 8PM.
The use of credit card
In Europe, credit cards are accepted but most stores prefer cash. As a matter of fact, you will be able to earn discounts if you use cash. Hence, before falling in love with what you see, you should ask first if credit card is accepted. Can you bargain? Of course yes, but it varies from one country to another. It is best to ask first if the price is negotiable. You know very well that haggling commonly takes place in the market.
When shopping, it would be convenient if you are going to bring your own shopping bag or else you will end up paying for a plastic bag to carry your stuffs with you. When in the grocery, the trend is to bag it yourself. Don’t expect that cashiers will bag your groceries for you.