Für diese Aufgabe brauche ich die doppelte Zeit.

German often puts a time phrase, place phrase, or other context at the beginning of the sentence to set the scene. Here, Für diese Aufgabe tells us what the statement is about: for this task.

Starting with that phrase gives it a little emphasis, as if saying:

As for this task, I need double the time.

It would also be possible to say:

Ich brauche für diese Aufgabe die doppelte Zeit.

Both are correct. The version with Für diese Aufgabe first sounds slightly more focused on the task itself.

This is because of the verb-second rule in German main clauses.

In a normal statement, the conjugated verb must be the second element. Since Für diese Aufgabe comes first, the verb brauche must come next, and then the subject ich follows.

So the structure is:

Für diese Aufgabe + brauche + ich + die doppelte Zeit

This is very common in German. Compare:

• Ich brauche für diese Aufgabe die doppelte Zeit.
• Für diese Aufgabe brauche ich die doppelte Zeit.

Both are correct, but the word order changes because the verb stays in second position.

The preposition für always takes the accusative case.

The noun Aufgabe is feminine, so the accusative feminine form is:

• nominative: diese Aufgabe
• accusative: diese Aufgabe

In this case, the form happens to look the same as the nominative.

If the noun were masculine, you would see the change more clearly:

• für diesen Job

So in für diese Aufgabe, diese is the correct accusative feminine form.

Here, für means for in the sense of for this task or to do this task.

It shows what the needed time is connected to.

So:

• Für diese Aufgabe = for this task
• or more naturally in English: to do this task

German often uses für in this kind of context when talking about what something is needed for.

Literally, die doppelte Zeit means the double time.

In natural English, that usually becomes:

• double the time
• twice as much time

So the sentence means that the speaker needs twice the amount of time for this task.

Because doppelte is an adjective describing the noun Zeit, and in German, adjectives before nouns usually come with an article or another determiner.

Here:

• die = the definite article
• doppelte = adjective
• Zeit = noun

So die doppelte Zeit is a noun phrase meaning the double amount of time.

This is a standard structure in German:

• die ganze Zeit = the whole time
• die gleiche Zeit = the same amount of time
• die doppelte Zeit = double the time

Because doppelte is the adjective form used before a noun.

Compare:

• die doppelte Zeit = the double amount of time
• doppelt so viel Zeit = twice as much time

In the sentence you were given, doppelte is modifying Zeit, so it needs the adjective ending -e.

You use doppelt without an ending when it works more like an adverb or part of a comparison:

• Ich brauche doppelt so viel Zeit. = I need twice as much time.

No, Zeit is usually treated as an uncountable noun, like time in English.

You normally say:

• mehr Zeit = more time
• weniger Zeit = less time
• die doppelte Zeit = double the time

Not usually Zeiten in this meaning.

The plural Zeiten does exist, but it usually means times in other senses, such as historical periods or repeated occasions.

Yes, absolutely. That is a very common and natural alternative.

Compare:

• Für diese Aufgabe brauche ich die doppelte Zeit.
• Für diese Aufgabe brauche ich doppelt so viel Zeit.

Both mean roughly the same thing.

A small difference:

• die doppelte Zeit sounds a little more compact and formal
• doppelt so viel Zeit sounds very natural and common in everyday speech

So as a learner, you should understand both.

Brauche is the present tense form of brauchen for ich:

• ich brauche = I need

German present tense often covers both simple present and near-future meanings, depending on context.

So this can mean:

• I need double the time for this task
• or, depending on the situation, I will need double the time for this task

Here, brauchen is just a normal main verb meaning to need.

The structure is straightforward:

• ich brauche etwas = I need something

In this sentence, the something is:

die doppelte Zeit

So the pattern is:

• Ich brauche mehr Zeit.
• Ich brauche die doppelte Zeit.
• Ich brauche für diese Aufgabe mehr Zeit.

Nothing unusual is happening with the verb here.

Yes, it is correct and natural.

That said, in everyday conversation, many speakers might also say:

• Für diese Aufgabe brauche ich doppelt so viel Zeit.
• Ich brauche für diese Aufgabe viel mehr Zeit.

The original sentence is perfectly good German, and it sounds clear and idiomatic. It may feel slightly more formal or precise than some everyday alternatives, but it is absolutely natural.