Admittedly, this was a very long time ago and all the German I've had any contact with in the last thirty years - despite having a family member who comes from Austria - has been subtitled programmes on SBS, the Australian national television channel which caters for non-English speakers as part of its remit, and I've had even less to do with French.
Still I thought the basics of German at least would still be there and initially I was right. I powered through the first ten sections, testing out after a few lessons. It was great. Then I realised that I wasn't retaining all the changes in the language - and there were many since I had last done any German study. Some were subtle variations in nuance but some were more dramatic. There were words that hadn't even been thought of - computers and health insurance, anyone - and others that had changed in usage or even spelling.
French was even worse. I found I remembered very little apart from greetings, counting one to ten and basics like please and thank you. Testing out was a fantasy because, although I often did, it was not based on any real understanding. Actually, it was often more luck than anything else.
So I went back to basics in both languages and started over. Now I resist the addictive urge to keep on doing lessons - one of the most appealing things about Duolingo is the way the lessons are structured so it feels like a game and it's very easy to get caught up - and make myself really learn each section. This means I've slowed down dramatically in my progress up the "tree" but it also means I have a much better grasp of the language. I'll probably take another year to reach the end of the course but that's okay because I'll have a good understanding of the language.
So is Duolingo the perfect learning system for languages? I can only speak for myself here but, much as I am enjoying my experience, as far as I'm concerned there are a few things I'd like to see changed. Because it is immersion - you read, hear and practise speaking the language and are supposed to learn it from that - very little grammar is explained and, for me, that doesn't always work. There is a comment section and there are knowledgable moderators in each language who answer questions in this section but the answers can get lost in lengthy threads. I need to know why something works as it does and that's meant tracking down other sources. Not an insurmountable problem in these days of internet searches - all Duolingo students have their own favourite links and many share them with the community - but one extra step to factor in. I'd like to see a comprehensive list of all the words I've learned, too, something that was there but has been removed for some reason.
That aside, there's much to like. It's free, there's an inclusive and supportive community, the lessons are fun and I've learned an immense amount in a relatively short time. I recommend it highly.