I agree with everything you recommend, but it is possible to speak grammatically with near perfection much faster than years if you study the grammar. Finding the right grammar book/course may not be easy. I was lucking enough to go through the excellent German course at UCSB in the late '70s before I immersed myself. Getting all noun genders right in German is nearly impossible for a non-native speaker (even native speakers make mistakes). Plus when you study the grammar you can delight educated native speakers by pointing out how the colloquial diverges from the proper grammar.