Halli-hallo! :) Thank you!
I wasn’t born in Munich, but I am German, born and raised. I wasn’t raised bilingually or anything, I just started reading books in English from an early age. For some reason, I liked that language better. I spent 9 months in the US, but most of what I know comes from writing in English for the past 5 years and looking up lots of vocabulary, grammar, etc. in the process. My spoken English isn’t nearly as polished. Oh, I also switched to watching every show, movie, etc. in English at some point. Languages work the best when you immerse yourself in them. Change your phone to English, etc. I feel like the more in touch you are with the language every day, the better. If you live in the US, I feel most of what you seek will come with time. For vocabulary etc., read lots of books!