Jag gjorde ett misstag.

Because göra (to do / to make) is an irregular verb.

Its forms are:

• att göra — to do / to make
• gör — do / make, present tense
• gjorde — did / made, past tense
• gjort — done / made, supine/past participle form in some uses

So Jag gjorde ett misstag uses the correct past tense form: gjorde.

In Swedish, göra can cover both do and make in many situations.

So:

• göra ett misstag = make a mistake
• göra läxan = do the homework
• göra kaffe = make coffee

This is normal Swedish usage. You just have to learn which noun combinations go naturally with göra.

Because misstag is a neuter noun in Swedish, also called an ett-word.

So the indefinite singular is:

• ett misstag — a mistake

Not all nouns referring to abstract things are ett-words, so this has to be learned with the noun.

A useful habit is to learn Swedish nouns together with their article:

• ett misstag
• en bok
• ett hus

The a is already built into ett.

So:

• ett misstag = a mistake

In Swedish, the indefinite article comes before the noun, just as in English:

• en bok = a book
• ett hus = a house
• ett misstag = a mistake

This sentence is singular because it says ett misstag — one mistake / a mistake.

If you wanted the plural, you would say:

• Jag gjorde misstag — I made mistakes

But the singular version is extremely common when talking about one specific error or admitting fault in a general way:

• Jag gjorde ett misstag — I made a mistake

Yes, Jag gjorde ett misstag is completely natural and idiomatic.

Other common possibilities are:

• Jag gjorde fel — I did wrong / I made a mistake
• Det var mitt fel — It was my fault
• Jag begick ett misstag — I committed a mistake

That last one, begick ett misstag, is more formal or literary. In everyday speech, gjorde ett misstag is very normal.

Yes, in this basic sentence the word order is very similar to English:

• Jag — subject
• gjorde — verb
• ett misstag — object

So it follows a simple subject + verb + object pattern:

• Jag gjorde ett misstag
• Hon köpte en bok
• Vi såg en film

This makes it a very beginner-friendly sentence.

Yes, and that is also very common.

The difference is:

• Jag gjorde ett misstag — I made a mistake

  • simple past
  • often tells about a completed event in the past

• Jag har gjort ett misstag — I have made a mistake

  • present perfect
  • often suggests the mistake is relevant now

In many situations, both can work, but the nuance changes slightly depending on context.

A rough learner-friendly pronunciation is something like yor-deh, but not exactly.

A few important points:

• The gj at the beginning is pronounced like a soft y-sound.
• The o is not a strong English oh.
• The stress is on the first syllable: GJOR-de

So you can think of it approximately as YOR-deh until you hear native pronunciation and refine it.

A rough approximation is MISS-stahg.

Helpful points:

• Stress is on the first syllable: MIS-stag
• The i is short
• The final g is pronounced, unlike in some English words

So a beginner-friendly version is MISS-stahg.

Because Swedish does not copy English vocabulary or grammar word-for-word.

You need the Swedish subject, verb, and noun phrase:

• Jag = I
• gjorde = made/did
• ett misstag = a mistake

So the whole sentence must be built in Swedish, not by inserting English words into a Swedish structure.

Yes, but it changes the meaning.

• Jag gjorde ett misstag = I made a mistake / one mistake
• Jag gjorde misstag = I made mistakes in general

Without ett, the noun is interpreted more generally or plurally depending on context. If you mean one mistake, keep ett.

Yes. You can count mistakes in Swedish just as in English.

Examples:

• ett misstag — one mistake
• två misstag — two mistakes
• många misstag — many mistakes

That is why ett misstag works naturally in this sentence.