Hi friends
I think I have a not-so-common problem for ESL with my language skills. I was born and bred German but live in the States.
My English is what most would perceive as pretty fluent. I work here and communicate daily, but at home we keep the German up for our kids, they would lose it too quickly. My kids are high school students.
Unfortunately my English still shows typical German patterns. It's not the pronounciation I worry about, as *** accents are most welcome. It's simply that native speakers can still detect some mistakes in my writing. For those who know Germans they even can detect that I am German by my writing. In speaking it's excusable, but not in writing.
Of course, nobody would correct or help me. They just say they have an inkling. Sometimes it's so subtle that they only know something was odd not wrong, just a little off. or they are just polite

That makes it difficult. I am not talking about the common mistakes, it's far more subtle and I have no idea how to tackle the issue. Even taking the typical ESL course won't help as I'm far too advanced for most or even all what is out in my area.
Anybody have an idea or resource?
Thanks in advance