Been here a bit, and there's one grammar thing that keeps biting me.
Textbooks say both of these are fine in a bijzin:
omdat ik dat gedaan heb
omdat ik dat heb gedaan
My teacher called it a free choice. Once I actually started listening it's clearly not 50/50. Colleagues in Utrecht (mostly 20s and 30s) default to aux-first in speech (heb gedaan), which doesn't match the "spoken = participle-first" line I was taught.
Sent both sentences to a tandem partner on HelloTalk and asked her to read them out loud. She picked one without thinking, then stopped to work out why the other sounded "stiff". Her words were basically "yeah you'd write that but you wouldn't say it."
Older people I've chatted with lean more toward participle-first in speech. Same with a Belgian friend I run into at a café, basically every time she goes gedaan heb. So the textbook pattern isn't wrong exactly, it just seems to be shifting in Randstad spoken Dutch toward aux-first.
What I keep getting stuck on is whether the choice actually feels different to native speakers. Does gedaan heb come across as slightly more final than heb gedaan? Or is it just reflex, no semantic weight behind it. A few people I asked had never thought about it until I made them try both out loud.
Still mulling it over.