Under cover cops? (Took place in Germany/ Lowersaxony )

(This took place in Germany/ Niedersachsen)

Me and my friend were smoking (we are both underage) and two people came up to us (a man and a woman) claiming they were undercover police. They wanted our IDs and told us that if we don’t comply they will call the police. I said that I don’t believe them and the man showed me his weird paper Police ID. After talking we both gave them our IDs and Adresse. Also they were constantly saying that we were lying and when I said that we will just go , he almost grabbed me and had a demanding tone. They said that we will maybe get a fine send to us and that they didn’t know how much it will be. We both think it’s not real and a scam but we want to make sure. (Pictures of the alleged undercover cops below)