Vi kører ind på en tankstation for at købe benzin og lidt vand til turen.

In Danish, the present tense often covers both the simple present and the present continuous.

So Vi kører can mean:

• We drive
• We are driving

In this sentence, the context makes it sound like we are driving or we’re pulling in.

The verb at køre usually means to drive, to ride, or to go by vehicle, depending on context.

Kører ind på means something like drive into, pull into, or drive onto.

Here:

• kører = drive
• ind = in / into
• på en tankstation = onto / into a gas station area

So the whole expression suggests entering the area of the gas station, not just heading toward it.

A useful comparison:

• Vi kører til en tankstation = We drive to a gas station
• Vi kører ind på en tankstation = We pull into a gas station

Danish often uses på with places that English might not think of as literally on something.

With tankstation, på is the normal preposition when talking about being at or entering the gas station area.

So:

• på en tankstation = at a gas station / onto a gas station forecourt

Using i en tankstation would sound strange here, because you are not thought of as being inside a tank station in the same way you would be i et hus (in a house).

En tankstation is the indefinite form: a gas station.
Tankstationen is the definite form: the gas station.

The sentence uses en tankstation because it introduces the place as just one gas station, not a specific one already known to the listener.

Compare:

• Vi kører ind på en tankstation = We pull into a gas station
• Vi kører ind på tankstationen = We pull into the gas station

For at + infinitive is a very common Danish structure meaning in order to or simply to when expressing purpose.

So:

• for at købe = to buy / in order to buy

The sentence is saying why they are pulling into the gas station.

Examples:

• Jeg gik ud for at handle. = I went out to shop.
• Hun ringede for at spørge om noget. = She called to ask about something.

Benzin is an uncountable noun, like water, milk, or money in English.

So Danish normally does not use en/et with it when you mean the substance in general.

That is why:

• købe benzin = buy petrol / gas

Not:

• købe en benzin

If you were talking about a countable item, you would use an article:

• købe en bil = buy a car

Lidt means a little or some.

Since vand is also uncountable, Danish uses lidt to show a small quantity:

• lidt vand = a little water / some water

This is similar to:

• lidt kaffe = a little coffee
• lidt tid = a little time

If the noun were countable plural, Danish would often use nogle instead:

• nogle flasker vand = some bottles of water

Turen is the definite form of tur, so it means the trip.

Here, til turen means for the trip. It refers to the specific trip the speakers are currently on.

So:

• til turen = for the trip
• til en tur = for a trip

Because the trip is already understood from the situation, Danish uses the definite form.

Og simply means and.

It connects the two things being bought:

• benzin
• lidt vand

So:

• købe benzin og lidt vand = buy petrol/gas and a little water

It works just like English and.

Yes, it is very normal.

The structure is:

• Vi = subject
• kører = finite verb
• ind på en tankstation = direction/place phrase
• for at købe benzin og lidt vand til turen = purpose phrase

So the sentence follows standard main-clause word order:

• subject + verb + the rest

The purpose phrase with for at købe comes naturally at the end.

Yes, depending on context, a natural English translation might be:

• We stop at a gas station to buy gas and some water for the trip.
• We pull into a gas station to buy gas and some water for the trip.

The Danish wording is more literally about driving into the gas station area, but in natural English, stop at or pull into may sound better than a very literal translation.

Yes. Benzin means petrol in British English and gasoline / gas in American English.

So:

• British English: buy petrol
• American English: buy gas

Be careful: Danish benzin is a liquid fuel, not gas in the scientific sense.

Tur is a common noun with en as its article:

• en tur = a trip

The definite singular is formed by adding -en:

• turen = the trip

This is very common in Danish. The definite article is usually attached to the end of the noun.

More examples:

• en bil → bilen = the car
• en station → stationen = the station
• en tankstation → tankstationen = the gas station

Yes, that is exactly the natural idea.

Vand til turen means water for the trip, in the sense of water they want to have with them during the trip.

So it is not just water connected abstractly to the trip. It strongly suggests practical use: something to drink on the way.