Hvis den forkerte tast er for tæt på, laver jeg hurtigt en fejl.

Hvis means if and introduces a condition.

So Hvis den forkerte tast er for tæt på ... means If the wrong key is too close ...

A useful distinction for English speakers is:

• hvis = if / whether
• da / når can sometimes mean when, depending on context

Here, the speaker is describing a condition: if the wrong key is too close, I quickly make a mistake.

This is a very common Danish word order pattern.

Danish is a V2 language in main clauses. That means the finite verb usually comes in the second position.

The sentence is structured like this:

• Hvis den forkerte tast er for tæt på = subordinate clause
• laver jeg hurtigt en fejl = main clause

Because the sentence begins with the if-clause, that whole clause takes the first position. Then the finite verb in the main clause must come next:

• Hvis ..., laver jeg ...

If you started directly with the subject, you would say:

• Jeg laver hurtigt en fejl, hvis den forkerte tast er for tæt på.

So:

• Hvis ..., laver jeg ... = correct
• Hvis ..., jeg laver ... = not correct in standard Danish

Den forkerte tast literally means the wrong key.

Breakdown:

• den = the for a common-gender noun
• forkerte = wrong / incorrect
• tast = key (as on a keyboard)

In Danish, when an adjective comes before a definite noun, you usually use:

• den/det/de + adjective + noun

So:

• en tast = a key
• tasten = the key
• den forkerte tast = the wrong key

You cannot normally just say forkerte tast for the wrong key. The den is needed.

Because the adjective is used in the definite form.

Compare:

• en forkert tast = a wrong key
• den forkerte tast = the wrong key

When an adjective comes before a noun that is definite, Danish usually adds -e to the adjective:

• en stor bil = a big car
• den store bil = the big car

So here:

• forkert becomes forkerte

That is why den forkerte tast is correct.

For tæt på means too close.

Breakdown:

• for = too
• tæt = close
• på = to / near

In Danish, tæt på is a common expression meaning close to or near.

Examples:

• Det er tæt på. = It is close.
• Huset ligger tæt på skolen. = The house is close to the school.

So in your sentence, er for tæt på means is too close.

Even though English often just says too close, Danish commonly uses tæt på as a unit.

Good question. The object is understood from the context.

Den forkerte tast er for tæt på really means something like:

• the wrong key is too close by
• the wrong key is too close to the one I want to press

Danish often leaves things unstated when they are obvious from the situation. Since we are talking about keyboard keys, the listener understands that the wrong key is too close to the intended key or finger position.

So the sentence is natural even without explicitly saying what it is close to.

The normal expression is lave en fejl, which means make a mistake.

So:

• jeg laver en fejl = I make a mistake

English speakers often want to use something like do a mistake, but English uses make a mistake, and Danish does too with lave.

Gøre en fejl is not the normal standard expression here. If you want the usual idiomatic Danish, use:

• lave en fejl

You may also see:

• begå en fejl = commit a mistake / make an error

That sounds a bit more formal or serious.

Hurtigt means quickly.

Here it modifies the verb phrase:

• laver jeg hurtigt en fejl = I quickly make a mistake

Its position is natural in Danish. Adverbs like hurtigt often come after the finite verb and subject, especially in a main clause like this.

Compare:

• Jeg laver hurtigt en fejl.
• Hvis ..., laver jeg hurtigt en fejl.

You could sometimes move adverbs around for emphasis, but hurtigt in this position is the most neutral and natural.

Because Danish often uses the indefinite article when talking about a single countable thing.

• en fejl = a mistake
• fejl = mistakes / error(s) in a more general or mass-like sense, depending on context

So:

• Jeg laver en fejl = I make a mistake
• Jeg laver fejl = I make mistakes

In your sentence, the speaker means a single mistake happens quickly, so en fejl is the natural choice.

Yes. Tast is a normal word for a key on a keyboard or keypad.

Examples:

• en tast = a key
• Enter-tasten = the Enter key
• tryk på en tast = press a key

Be careful not to confuse it with words related to taste in English. Danish tast has to do with keys, buttons, and typing.

You can say:

• Jeg laver hurtigt en fejl, hvis den forkerte tast er for tæt på.

That means the same thing.

The difference is mostly in information structure:

• Hvis den forkerte tast er for tæt på, laver jeg hurtigt en fejl.
  This emphasizes the condition first.
• Jeg laver hurtigt en fejl, hvis den forkerte tast er for tæt på.
  This starts with the result first.

Both are natural. The original sentence simply chooses to foreground the if-clause.