Hvis pletten ikke går af med en klud, tager jeg en skuresvamp.

In this sentence, hvis means if in the sense of a condition:

• Hvis pletten ikke går af ... = If the stain doesn’t come off ...

Danish om can sometimes mean if, but it is usually used more like whether:

• Jeg ved ikke, om det virker = I don’t know whether it works

So here, because the sentence sets up a condition, hvis is the natural choice.

Plet means stain or spot.

Pletten means the stain. The ending -en is the Danish way of making many common-gender nouns definite:

• en plet = a stain
• pletten = the stain

This is different from English, where the is a separate word. In Danish, the definite article is often attached to the end of the noun.

Går af here means comes off or can be removed.

The verb is gå af, which in this context is used about something separating from a surface:

• Pletten går af = The stain comes off

This is one of those verb combinations where the meaning is not just the simple meaning of gå (to go/walk). Danish often uses short verb + particle combinations like this, much like English uses come off, take off, wash out, etc.

Both word order and sentence type matter here.

Inside the hvis clause, Danish uses normal subordinate clause word order, where ikke usually comes before the finite verb:

• Hvis pletten ikke går af ...

Compare that with a main clause, where the finite verb usually comes before ikke:

• Pletten går ikke af = The stain doesn’t come off

So:

• main clause: verb before ikke
• subordinate clause: ikke before the verb

That is a very common Danish pattern.

Med en klud means with a cloth.

• med = with
• en klud = a cloth

It tells you the means or tool used to try to remove the stain.

So:

• går af med en klud = comes off with a cloth
• more naturally in English: comes off using a cloth / can be removed with a cloth

Both klud and skuresvamp are common-gender nouns in Danish, so they take en in the indefinite singular:

• en klud = a cloth
• en skuresvamp = a scrubbing sponge

In Danish, nouns are mainly either common gender or neuter:

• common gender: en
• neuter: et

So the article is determined by the noun’s grammatical gender, not by meaning.

Skuresvamp is a scrubbing sponge, scouring sponge, or sometimes just a scrubber.

It is a compound noun:

• skure = to scrub
• svamp = sponge

Danish makes compound nouns very freely, so learners often need to get used to reading them as one word.

This is because Danish main clauses normally follow the verb-second rule.

The first part of the sentence is a subordinate clause:

• Hvis pletten ikke går af med en klud

After that, the main clause begins:

• tager jeg en skuresvamp

In a Danish main clause, the finite verb usually comes in the second position. Since the hvis clause comes first, it takes the first slot, so the verb of the main clause comes next:

1. Hvis pletten ikke går af med en klud
2. tager
3. jeg en skuresvamp

If the main clause stood alone, it would be:

• Jeg tager en skuresvamp

But after a fronted clause, Danish inverts the subject and verb:

• Hvis ..., tager jeg ...

Danish often uses the present tense to talk about the future, especially when the meaning is clear from context.

So:

• Hvis pletten ikke går af med en klud, tager jeg en skuresvamp.

means something like:

• If the stain doesn’t come off with a cloth, I’ll use a scrubbing sponge.

This is very natural in Danish. English can do something similar too:

• If that doesn’t work, I use the stronger one
  though English usually prefers I’ll use here.

Yes, literally tage means take. But in this context, English would usually translate it more naturally as:

• I’ll use a scrubbing sponge
• I’ll get a scrubbing sponge

So Danish tage is often broader than English take. In everyday usage, it can mean something like take/use/pick/get, depending on the context.

Yes. It is a very common Danish pattern:

• Hvis
  • subordinate clause
• then a main clause with inversion

So the structure is:

• Hvis
  • subject + ikke
    • verb + rest,
      verb
      • subject + rest

In this sentence:

• Hvis pletten ikke går af med en klud, tager jeg en skuresvamp.

This pattern is extremely useful for building conditional sentences in Danish, for example:

• Hvis det regner, bliver jeg hjemme. = If it rains, I stay home / I’ll stay home.
• Hvis du har tid, kommer jeg forbi. = If you have time, I’ll stop by.

Yes. You can put the main clause first:

• Jeg tager en skuresvamp, hvis pletten ikke går af med en klud.

This means the same thing.

The difference is mainly about emphasis and flow:

• Hvis ... , tager jeg ... puts the condition first
• Jeg tager ... , hvis ... starts with the action instead

Both are natural Danish.