Less than Singapore for sure. Less than European cities, I’m not so sure. I don’t have the numbers but if you do an image search of Jakarta (probably one of the worst vegetation-wise and boasting a population of a quarter of Germany) it still has trees in every picture and many more than let’s say Frankfurt or Madrid. The latter has many photos without a single tree.
79% of all German trees are sick. Monocultures and beetles play a role but the problem is much bigger than that: https://www.bmleh.de/DE/themen/wald/wald-in-deutschland/wald...