I couldn't find any statistics about the frequency of spam calls in Germany, so I can only share my personal experience. I have never received a single one since having my own number. My parents got more when their number could still be found in the public phone book (yes, that is/was a thing). Friends complain maybe twice a year.

I am not a relevant example though, I am very cautious about giving out my number, usually I only do so when absolutely necessary and I often don't use services (like dating apps) if they don't let me without verifying my phone number.