Janet, I use Duolingo now for German (mostly for review) and have been using it off and on for the past five to six years, but to be honest, most of my German I learned in the classroom, either on Zoom during COVID or in person.
Most states, and maybe every state, have programs for senior citizens where you can take university classes (state schools only) for free or really cheap. The University of Minnesota offers classes that, at the time, were $10 a credit hour and now are $20, or you can audit it for free, so that's what I did. I parked myself in with a bunch of college freshmen and sophomores and was able to test out of German 1 because I had taken a class at the Germanic American Institute in Minneapolis, but then went the rest of the way through the program. By that point, I was able to take an upper-level class at the University of Minnesota at Duluth where nothing was spoken in class except German. That was a real test of my skill, and I was definitely on the lowest rung of that class, but it really helped.
I did like the Pimsleur program when I did it many years ago, but that was for travel, which I think is a different ballpark than language you use while living in the country. I wanted to learn conversational German so that I could really speak with people and have conversations. I've attained that to a certain extent. I'm still not anywhere near fully fluent, but I keep trying.
With regards to apps, I go on the language forums on Reddit a lot, and by far and away the app I've seen recommended the most is Langua. The people who are using it really like it, and it's gotten some good reviews online. Here's a couple of links to them if you'd like to check them out. I think Langua offers a free seven-day trial period. https://languatalk.com
https://thefabryk.com/blog/langua-review
https://tanyamozias.substack.com/p/langua-review-ai-language-learning
