I had a security job like this. I worked mornings on the weekend where 90% of the time it was only security on-site. The other half of my schedule was overnights Monday and Tuesday. Again, save for the occasional night, nothing ever really happened outside of shift change. Idk about Germany but here in the US a security license is only 40hrs and, to me, mostly common sense. I was also only paid $11/hr in 2020-2021. I have a feeling they want something that pays more than that.