I’ve heard Duolingo is useful if you are travelling to a new country and want to learn some phrases. You will not be conversational but it’ll help you get by.
I was told (long ago now) that the US State Department has some of the best language courses for their diplomats. A very fast Google found this which says it is for diplomats. Might be worth a look (I think it is free).
I’m in my 3rd year of studying French with only Duolingo. I knew nothing in French except the most common phrases: “Oui!” “Non.” “S’il vous plaît!” and so on when I started.
I don’t devote a lot of time to it, maybe 20-30 minutes a day.
As others have noted, it hasn’t done much to teach me how to speak French fluently. But I can read it much better now and even get the gist of spoken conversations. I’m about ready to seek out a conversational French meet-up group to practice speaking.
I feel like I’ve gotten quite a lot out of sticking with it.
This is a good way to learn to understand and speak the language you are studying (and if there are other non-native speakers in the group, it’s great because they tend to speak a lot slower than native speakers!)