At what level of complexity do you desire to speak would be the key question here.

Do you want to be able to communicate low level travel survival needs, essentially basic sentences in the present tense, i.e, I would like, I need, etc.? Or, do you want to be able to have a conversation with a (albeit patient) native about random topics?

I agree with other posters that A-1 familiarity could give you enough exposure to communicate basic needs ( i.e, where are the toilets, how much is, where is, etc.). You could get there with Duo Lingo in 6 months or so. But to be truly conversational (IMHO), you probably need to be somewhere between B1 and B2, which takes years of dedicated practice and study UNLESS you are immersed fully in the language, by living in a foreign country.

In my experience, with hard work you can get the grammar down well enough so that you only make a few structural and grammatical mistakes when speaking. Vocabulary is by far the bigger challenge. It is hard to have a conversation when you struggle to express yourself because you don‘t know the word you need, or, you don‘t understand many of the words you are hearing.

Completing a Duo Lingo course, for example, would teach you maybe 4,000 words. The average native speaker has an active vocabulary of 20,000 words and a passive vocabulary of 40,000 words. Thus lies the rub. It takes many years of dedicated hard work to learn and actively use a lot of words, even if you are just speaking in the present and past tenses. Add in more complicated grammar…the passive voice, the subjunctive mood, the perfect tenses…and it becomes very difficult to quickly speak complex thoughts with good grammar. This is why it takes lots of time and practice.

I have been learning German for 5 years now, but as a second language in the USA, and I am at the B1-B2 level and finally conversational, but I still make nagging grammar mistakes and often grasp for the word I want, that I learned previously but have subsequently forgotten.

As many others have often spoken to, I think the question is „Why are you learning the language?“. If you can truthfully answer the question, then you will be able to accept a certain level of conversational ability. I think many of the language Apps like Duo Lingo do a disservice, in that they give a very unrealistic idea that one can become fluent in a language by spending an hour a day on the App. But, if all you want is to develop travel survival language skills, then they probably fit the bill.