Your experience is not unusual.
I lost Korean at age 7-9, and relearned it all my life.
My Korean now is above most Koreans' except for the local dialects.
The comparative way of learning languages is probably one of the best ways to see the uniqueness of any particular language, I think!
Have fun. I can't seem to get it right. I always get confused using は OR が and the other particles I got a basic idea of how to use them. I just need more conversational practice to use the vocabulary I learned and forgotten.