What? I have to pay to use a shopping cart?!

Living here I knew I would make some bonehead american moves and yesterday was an occasion. Went grocery shopping at another store down the street. This time I wanted to use a shopping cart so I don't have to carry the weight until I have to. I went to grab a cart and saw that they were all chained together. I kept looking for a mechanism of some kind to unlock it but couldn't. I was trying to be inconspicious and not look so stupid struggling with a cart. I might as well where a sign that says "I'm not from around here!". I remember my first night here I went to REWE market and tried the same thing. Again the carts were chained together but at that late of day I thought they were just putting the carts away and chained them together for the night.. I didn't think much of it and just went and got a basket instead. Anyway, here I was in the same situation except it was early in the afternoon and there were people around. I was getting frustrated struggling to pull apart the cart when a man passed me with his cart with the intention of putting it back. I thought, perfect, great timing. I made the motion for him to give me his cart. At home this happens sometimes when you are done with your cart and someone is coming in and just takes your cart from you. Well, this man wouldn't give me his cart and again I made the motion for him to give it to me. He kept moving to put his cart away and I thought what a mean german he was. Why couldn't he just give me his damn cart! He was saying something to me but ofcourse I couldn't understand a word of it. He was smiling when he showed me that by putting his cart away he got a coin back. Oh, DUH! Apparently you put in a coin to get your shopping cart and you get the coin back when you put the cart away. By then I was too embarrassed to figure out exactly how much you have to put in since there were more people now. I just nonchalantly went into the store with the intent to just using the basket. Well, wouldn't you know it, I couldn't find a damn basket anywhere. Great, it's going to be a pain carrying my stuff while I shop. It was a sign when I couldn't find a lot of organic fruits and vegetables in this store. I decided to go back to REWE where at least I knew my way around and there was a basket for me to use. Oy vay, some of the simplest things are not so easy here. Next week I am determined to figure out the shopping cart and will bring lots of different coins with me!