What is the correct formation of verb plus infinitive?

Question

I want to say:

How long does it take to learn a new language?

I arrived at:

Wie lange braucht man um ein neu Sprache zu lernen?

Is the um ... zu formation correct here?

Answer 1

Yes, it is correct.

As a sidetone: be aware that Sprache is feminin, and that a question is usually closed by a question mark. Also, regarding an infitive clause introduced by um, it is mandatory to separate the clause by comma. Hence it must be:

Wie lange braucht man, um eine neue Sprache zu lernen?

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_{Just one comment on the necessity of the comma: Duden says that the comma is mandatory before infinitive clauses that are introduced by one of the words als, anstatt, außer, ohne, statt or um. See https://www.duden.de/sprachwissen/rechtschreibregeln/komma#D117 for the rule. (Since it is being discussed in the comments: For the general question of rules in German language, have a look at the discussion at Meta: Normative Fragen and at Welche normative Autorität hat der Duden? / What's the normative authority of the Duden?). Besides Duden, also the rules of the Rechtschreibrat, who decides on the rules being taught in school, says so (§75 of the linked document):}

Infinitivgruppen grenzt man mit Komma ab, wenn eine der folgenden Bedingungen erfüllt ist: (1) die Infinitivgruppe ist mit um, ohne, statt, anstatt, außer, als eingeleitet [...]