Jag brukar ta med en lunchlåda när jag jobbar på kontoret.

Brukar is used to talk about a habit or something that happens regularly.
So Jag brukar ta med en lunchlåda means I usually / generally / tend to bring a lunch box.

A very common pattern is:

brukar + infinitive

For example:

• Jag brukar läsa på kvällen = I usually read in the evening
• Hon brukar cykla till jobbet = She usually cycles to work

So here, brukar shows that this is not a one-time action, but a routine.

Because ta med is a fixed verb phrase meaning bring along / take with you.

• ta = take
• ta med = bring / take along

So:

• Jag tar en lunchlåda could sound like I take a lunch box
• Jag tar med en lunchlåda clearly means I bring a lunch box with me

This is very similar to English verb-particle combinations.

Examples:

• Hon tar med sin dator = She brings her computer
• Ska du ta med kaffe? = Are you bringing coffee?

Lunchlåda is a compound noun:

• lunch = lunch
• låda = box

Together, lunchlåda means lunch box, often referring to a packed lunch in a container that you bring from home.

Swedish uses compound nouns very often, and they are usually written as one word. So lunchlåda is one word, not two.

Other similar compounds:

• matlåda = food container / lunch box
• vattenflaska = water bottle
• kaffekopp = coffee cup

Because lunchlåda is a common-gender noun in Swedish, so it takes en, not ett.

In Swedish, nouns belong to one of two grammatical genders:

• en-words
• ett-words

låda is an en-word, so the compound lunchlåda is also an en-word.

So:

• en lunchlåda
• lunchlådan = the lunch box

This is something you usually have to learn with each noun.

Here, när means when in the sense of whenever or on the occasions that.

So: när jag jobbar på kontoret = when/whenever I work at the office

This fits well with brukar, because the whole sentence describes a repeated situation: I usually bring a lunch box when I work at the office.

In many cases, när is the normal word for when:

• När kommer du? = When are you coming?
• Jag läser när jag har tid = I read when I have time

Usually no, not with this meaning.

• när is used for when something actually happens or regularly happens
• om often means if or in (about future time)

So in this sentence, när is correct because the speaker is talking about a real, repeated situation:

• När jag jobbar på kontoret... = When/whenever I work at the office...

If you said om jag jobbar på kontoret, that would sound more like:

• if I work at the office
• possibly a condition, not a regular routine

Yes, you can say arbetar, but jobbar is more common in everyday spoken Swedish.

• jobbar = common, neutral, everyday
• arbetar = a bit more formal or written, though still very normal

So:

• Jag jobbar på kontoret sounds natural and conversational
• Jag arbetar på kontoret is also correct, but slightly more formal

Both mean I work at the office in this context.

In Swedish, på kontoret is the normal idiomatic way to say at the office or in the office when talking about working there.

Even though English often uses in, Swedish very often uses på for workplaces, institutions, and similar locations.

Examples:

• på kontoret = at the office
• på jobbet = at work
• på skolan = at the school in some contexts

So jag jobbar på kontoret is the natural Swedish expression.

Using i kontoret would usually sound wrong for this meaning.

Kontoret is the definite form of kontor:

• ett kontor = an office
• kontoret = the office

In Swedish, places like the office, the school, the hospital, and similar locations are often expressed with the definite form where English may or may not emphasize the.

So på kontoret is the standard expression for at the office.

This is very common:

• på jobbet = at work
• i skolan = at school
• på sjukhuset = at the hospital

Yes. In the original sentence, the main clause comes first:

Jag brukar ta med en lunchlåda
then the subordinate clause: när jag jobbar på kontoret

That gives: Jag brukar ta med en lunchlåda när jag jobbar på kontoret.

If you start with the när-clause, Swedish changes the word order in the main clause because of the V2 rule:

När jag jobbar på kontoret brukar jag ta med en lunchlåda.

Notice that it is:

• brukar jag not
• jag brukar

So the two versions are both correct:

• Jag brukar ta med en lunchlåda när jag jobbar på kontoret.
• När jag jobbar på kontoret brukar jag ta med en lunchlåda.

Yes. The exact English translation depends on perspective.

Swedish ta med focuses on taking something along with you, and in English that can be translated as either:

• bring
• take with me

So these can all work depending on context:

• I usually bring a lunch box when I work at the office
• I usually take a lunch box with me when I work at the office
• I usually bring my lunch when I work at the office

The Swedish sentence itself is completely natural.

Not always. In careful speech, jag is often pronounced roughly like yahg or ya depending on accent, but in everyday spoken Swedish it is often reduced.

Very commonly, jag sounds more like:

• ya
• sometimes even a very short ja-like form

So learners may hear:

• Jag jobbar... sounding almost like Ya jobbar...

This is normal spoken Swedish. The spelling stays jag, but the pronunciation is often reduced in everyday speech.

Yes, very often.

Matlåda is extremely common and often means a container of food that you bring with you, especially to work. In many situations, it may sound even more natural than lunchlåda.

• lunchlåda = lunch box
• matlåda = food box / lunch container / packed lunch

So a very natural alternative sentence would be:

Jag brukar ta med en matlåda när jag jobbar på kontoret.

That would mean almost the same thing in everyday Swedish.