Jag vågar inte stå högst upp på stegen, men min syster använder stegen utan problem.

Because this is a main clause, and in Swedish the finite verb usually comes in second position. Here, vågar is the finite verb, so it comes right after Jag, and inte follows it:

• Jag vågar inte ...

This is very common in Swedish:

• Jag kan inte komma.
• Hon vill inte äta.

If it were a subordinate clause, the position of inte would usually be different:

• ... att jag inte vågar stå högst upp på stegen.

Because våga is often followed directly by the infinitive, without att, especially in modern everyday Swedish.

So:

• Jag vågar stå där. = I dare stand there / I dare to stand there.

This is similar to modal-verb-like patterns in Swedish, where the second verb stays in the infinitive without att.

You may sometimes see våga att in certain styles or contexts, but vågar stå is the most natural choice here.

Vågar is the present tense of våga, which means to dare.

So:

• Jag vågar inte ... = I don’t dare ...

It often expresses lack of courage, confidence, or willingness because something feels scary, risky, or uncomfortable.

Examples:

• Jag vågar inte hoppa. = I don’t dare jump.
• Hon vågar fråga. = She dares to ask.

Högst upp means highest up or more naturally here at the very top.

It is a common Swedish expression:

• upp = up
• högst = highest

Together, they mean something like:

• at the top
• all the way up
• highest up

Examples:

• Boken ligger högst upp på hyllan. = The book is at the very top of the shelf.
• Han bor högst upp i huset. = He lives at the top of the building.

So in your sentence:

• stå högst upp på stegen = stand at the very top of the ladder

Swedish uses på because you are standing on the ladder.

• på = on
• stegen = the ladder

So:

• stå på stegen = stand on the ladder

This matches the physical idea that your feet are on the rungs of the ladder.

Compare:

• på stolen = on the chair
• på taket = on the roof

In this sentence, stegen means the ladder.

That is because it comes from en stege:

• en stege = a ladder
• stegen = the ladder

But you are right to notice that stegen can also look like the definite plural of steg:

• ett steg = a step
• stegen = the steps

So stegen can be ambiguous by itself. Context tells you which meaning is intended.

Here, because of:

• stå högst upp på stegen
• använder stegen

the meaning is clearly the ladder.

Because after a possessive word like min, din, hans, hennes, vår, and so on, Swedish normally uses the indefinite form of the noun.

So:

• min syster = my sister
• not min systern

Compare:

• min bok = my book
• hans bil = his car
• vår lärare = our teacher

This is different from English logic, because English often combines my with what feels like a definite meaning. In Swedish grammar, though, possessives usually go with the noun’s indefinite form.

Men means but and joins two contrasting clauses.

The contrast is:

• I don’t dare stand at the top of the ladder
• but my sister uses the ladder without any problem

So men highlights the difference between the speaker and the sister.

This is a very common coordinating conjunction:

• Jag är trött, men jag måste jobba.
• Han vill gå, men hon vill stanna.

Because använder stegen means uses the ladder, which is a broader idea than just stands on the ladder.

The sentence is saying that the sister has no problem using the ladder in general. That could include:

• climbing it
• standing on it
• working on it

So använder makes the statement more general and natural.

• använder = uses
• står på stegen = stands on the ladder

The first clause focuses on one specific fear: being at the top.
The second clause gives a broader contrast: the sister handles the ladder just fine.

Utan problem means without problems or more naturally without any problem / no problem.

So:

• min syster använder stegen utan problem = my sister uses the ladder without any problem

It is a very natural expression in Swedish.

You could also say things like:

• Hon klarade det utan problem. = She managed it without problem.
• Han gjorde det utan några problem. = He did it without any problems.

Compared with inga problem:

• inga problem often works more like no problems
• utan problem means without problems

Both are possible in some contexts, but utan problem fits very naturally after a verb like använder.

The sentence is in the present tense.

The present-tense verbs are:

• vågar = dare
• använder = use / uses

So the sentence describes a present or general situation:

• I don’t dare ...
• my sister uses ... without problem

Swedish present tense is often formed with -r:

• våga → vågar
• använda → använder

Yes, that is close literally, but it sounds less natural in everyday English.

A more natural English translation would be:

• I don’t dare stand at the top of the ladder or
• I don’t dare stand on the top of the ladder

The Swedish phrase högst upp is very idiomatic, so it is usually better translated naturally rather than word-for-word.

Yes. This is normal main-clause word order.

The structure is:

• men = but
• min syster = subject
• använder = finite verb
• stegen = object
• utan problem = adverbial phrase

So the basic order is: subject + verb + object + adverbial

That is the standard pattern in simple Swedish main clauses.

Yes, in many contexts överst could work, because it also means at the top or topmost.

For example:

• Jag vågar inte stå överst på stegen.

That sounds natural too.

A small nuance:

• högst upp often emphasizes highest up
• överst often emphasizes at the top position

In this sentence, both are possible, but högst upp på stegen sounds very natural and clear.

Swedish often repeats the noun when that sounds clearer and more natural.

So:

• Jag vågar inte stå högst upp på stegen, men min syster använder stegen utan problem.

This is clear and perfectly normal.

You could sometimes rephrase to avoid repetition, but here repeating stegen is not strange at all. It keeps the contrast easy to follow:

• I am afraid of the ladder
• my sister is not

In many real sentences, Swedish repeats nouns a bit more readily than English does.