That thing about automatically reverting to the last language you learned when you forget a word is LEGIT.
In high school, I lived in Germany for nine months (long story) before moving back to the US, like, a week before school started. There was no international school in the extremely small Bavarian town where we’d lived (again, long story) so I went from essentially auditing high school in a completely German-speaking curriculum (I did not speak German and was frantically trying to pick it up from immersion, it’s a LONG story) to being back in an American high school.
I had, previously, been learning Spanish since kindergarten but my teachers were not good, so I never really progressed past introductory-level.
God bless my junior-year Spanish 1 teacher, honestly, and I’m extremely lucky that the woman was a genius who spoke like seven languages fluently (she left after that year and became a college professor) because.
I got an A+ on my Spanish final. Then, on the last day of school, she pulled me aside and told me very kindly that she gave me full credit on my essay, which was 50% of the final grade, because I did an excellent job, showed off a lot of vocabulary, and all of my sentences and conjugations were absolutely correct and in the proper tense…
“I just need you to be aware that you did write half of it in German. I’m not taking points off because it was GOOD German, and I could understand it, and I understand why that was happening, but I did want to make sure you know you’re doing that for next year.”