Every short haul FO that I know makes more.
Then you don't know any FOs from Aerologic
If you are a wide body CPT you will make about 8500-9000€ flying 60h per month. Depending on your experience it will be more, about 10.000€ flying 90h plus per diems. NLH Cpt makes about 10500€ including per diems, so not great, but not that bad.
42% taxation applies to the income above 54.000€ up to 260.000€
The german tax system isn't that easy, but I guess that most of the people they are hiring are german, so they know about it.