Secondhand anecdotes about learning a new language

I have a friend who learned German while she was living in Germany for a year.

She said she went through these stages:

Being overwhelmed by everyone speaking German so quickly
Beginning to understand what other people were saying
Beginning to speak German
Not knowing a certain word in German, but knowing it in English
Not remembering a certain word in German or English
Not remembering a certain word in English but remembering it in German
Being able to speak both languages well

She also told me about a conversation she had with a German-speaker on a plane. She could speak German but could listen easier than she could speak. The German-speaker was the same for English. So they were having a really in-depth political conversation on a plane in two different languages! She would say something in English and get a response back in German. Apparently they had a really long conversation, and understood each other really well, but everyone sitting near them was super confused about what was happening! LOL.