Anything between 2 and 200 months and for some people it just doesn't ever happen :-)

In other words this depends on so many things that it cannot be answered.

I can only answer for myself. I studied German in high scool and college; I didn't get to understand German until I lived in Berlin and had to speak it every day. I found that reading German was a big help. Ich wuensche dir viel Erfolg.

German is quite a difficult language (unless you are Russian :-) /end-joke).

I could read adult books comfortably in Italian, French, Portuguese and Catalan just after 6-10 months, but German has taken me two years and a half to reach that stage, and still my reading speed in German is slower than in the other languages (I have completed four German trees here, and still my speaking level is that of a 3-4 years old :-) ).

So...yes, it takes some time :-)

Well, I can tell you that there is no bar. You just need to listen to German a lot. Look up Extr@ deutsch lernen on Youtube. It is very cheesy, but I used it, and I am way better at picking out words and stuff. Listen and watch, and listen and watch again. Rewatching and listening is the best you can do to pick out phrases, and ultimately understand conversations clearly. If you do this and you have a basic understanding of German vocab, you should be able to at least piece the sentences together. If you do this every day listening to the same episode twice, or even better, three times, you will be able to start conversing, and understanding someone better. I would also recommend that you start deconstructing words, like abgeben, which means to submit (like homework submit). Can you see the geben in there? That means to give. Once you have the basic ingredients, you should know the rest. I would say within a month of constantly listening to these episodes, and thinking more in German, you should have the basic sentence structure down, and you should understand more.

BliuBliu talked about 30 days challenges (seems they do not offer anymore at this time).
Benny Lewis says "Fluent in 90 days" - you can find the conversation connector courses on Memrise.

So it is (should be) days, not months :-)

Joking byside.........well, depends on you.
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• How many hours do you practice DAILY?
• What is your personal and language background?
• How do you practice German?
• What tools do you use? Only DuoLingo?
• Do you have (full) Immersion?
• Are you going to practice any listening and reading?

A first guess:

1-2 years do quickly pass, if you have to start to learn a language totally from scratch.

A DuoLingo tree might take you +-1 year (I have seen reports about longer times or even half or full STOPS for German).

After you have finished it, you can not write well (you need the reverse tree) or speak the language (e.g nested sentences)- this is my PT BR experience - learning from scratch and still searching for the proper "tools".

When you have finished your forward tree EN-DE, you probably can not 100% listen to German TVs, radios, Youtube and fast spoken sentences.
This might take you another 6+ months to develop those skills.

Examples:

I am learning Portuguese BR (Duo, Memrise, Mondly, uTalk, 50languages, etc.) since about 1,4 years and I would not say that I do understand it "properly"....nor that I am "fluent" in writing or speaking.
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How much Spanish would I understand after learning 1000 words in 20 hours in 11 days on Lingvist? (Probably) not too much...even with my Portuguese skills.

So many things to learn, grammar to strengthen, especially tenses, etc.

I would not expect that German is any different for you.

Start slow - be patient - take your time to progress.

The faster you progress - the more expectations you put on your side - the faster and higher you can fall.

http://how-to-learn-any-language.com/e/languages/german/index.html
http://how-to-learn-any-language.com/e/languages/similarities/german/index.html

I'm near the end of the course, and I started in November with nearly no prior knowledge of the German language. It takes a long time to understand, but even more to speak. I say a few years or more to speak, maybe one year to fully understand.

it's taken me at least 3 years, and i am still not fluent. i am taking a german course in my school and only somewhat understanding it. as a native english speaker, one would think it would be easy for me? i find turkish very easy for me, which is why i'm learning it. i suppose it's how willing someone is to learn the language, added onto the fact it might be easier to learn a language related to one's native.

i have seen many foreigners coming to germany without knowing even one word in the the beginning. many of them where able to converse afte a short time ( like 6 months) but where there also people living in germany for more than 20 years who still could'nt. the reason was simply put the first group of people where making contact with lokals. the second did'nt. i think only a few people will be able to understand german at all if do not have german speaking friends.

For me it didn't take that long but yeah for some it could take years you kinda need to like have a photographic memory

Never