Or Duolingo. It’s free.
I didn’t have much off duty time to take those classes my first two years, was pulling duty officer usually twice a week. I had more free time when I was kicked up to Battalion staff.
Shortly after I attended those classes, I was sent TDY to a German firing range for 3 months. We were the only Americans for 200 miles. I was nearly fluent after that. I’ve forgotten most of it, though.