Hey Alexander, I worked with Ilhan on this, so I can tell you we use SignalHire to get personal emails (and if that doesn’t work, we use one of the Clay personal email waterfalls).
I work with another client who operates in the German market, and I haven’t found any reliable source of personal emails. This varies significantly depending on the industry, but Germany is notorious for data protection laws, and people, in general, are more protective of their personal data.
We were more successful with work emails if that’s something you can consider. Hope that helps, and feel free to message me if you have additional questions