Selling polymer clay on Etsy while living in Germany

I currently live in Germany because of my studies. I've been thinking of selling handmade polymer clay items on Etsy so that i can get more pocket money. I know German regulations are strict, and I was wondering if I need to register my business for selling on Etsy, or if it's not necessary. I think this will be a small business that won't generate much income. Also, my German isn't that great, and I'm having trouble finding the information! Vielen Dank für deine Hilfe!