Hvis vi løber tør for kaffe, vil vi drikke te i stedet.

This is very normal in Danish. After hvis (if), Danish often uses the present tense to talk about a possible future situation.

So:

• Hvis vi løber tør for kaffe = If we run out of coffee
• not literally If we will run out of coffee

This works a lot like English, where we also usually say:

• If we run out of coffee, ...
• not If we will run out of coffee, ...

So løber is present tense, but the whole clause can still refer to the future.

Løbe tør for is an idiomatic expression meaning to run out of something.

In this sentence:

• vi løber tør for kaffe = we run out of coffee

The parts are:

• løber = run / are running
• tør = literally dry
• for = of / for

But you should learn løbe tør for as a fixed expression, not word by word. Its real meaning is simply to have no more left.

You can use it with many nouns:

• Vi er løbet tør for mælk. = We’ve run out of milk.
• Han løb tør for penge. = He ran out of money.

This is because of the Danish V2 word order rule in main clauses.

In a Danish main clause, the finite verb usually comes in the second position. When the sentence starts with a subordinate clause like Hvis vi løber tør for kaffe, that whole clause takes the first position. Then the finite verb of the main clause comes next:

• Hvis vi løber tør for kaffe, vil vi drikke te i stedet.

Structure:

• Hvis vi løber tør for kaffe = first position
• vil = finite verb in second position
• vi = subject

So Danish does not keep the English order here. English says:

• If we run out of coffee, we will drink tea.

But Danish says:

• Hvis ..., vil vi ...

Vil often means will and is commonly used to express the future.

Here:

• vil vi drikke te = we will drink tea

So the sentence describes what will happen in that situation.

However, Danish often uses the present tense for future meaning too, depending on context. So in some situations you might also hear:

• Hvis vi løber tør for kaffe, drikker vi te i stedet.

That can also mean If we run out of coffee, we’ll drink tea instead.

Using vil makes the future/result a bit more explicit.

Yes, that is possible.

Both versions are natural:

• Hvis vi løber tør for kaffe, vil vi drikke te i stedet.
• Hvis vi løber tør for kaffe, drikker vi te i stedet.

The version with vil sounds a bit more explicitly future-oriented: then we will drink tea.

The version without vil is also common and can sound a little more like a general plan or usual result.

In many everyday contexts, both would be understood the same way.

Because kaffe and te are being used as uncountable mass nouns, just like in English.

So Danish says:

• kaffe = coffee
• te = tea

not usually:

• en kaffe
• en te

in this kind of sentence.

Here the meaning is about the substances in general, not one cup or one serving.

Compare:

• Vi drikker te. = We drink tea.
• Jeg vil have en kaffe. = I want a coffee.
  This usually means a cup of coffee.

I stedet means instead.

So:

• vi vil drikke te i stedet = we will drink tea instead

This means tea is the alternative choice.

I stedet for means instead of and must be followed by what is being replaced:

• Vi drikker te i stedet for kaffe. = We drink tea instead of coffee.

So:

• i stedet = instead
• i stedet for + noun/pronoun = instead of ...

In your sentence, i stedet is enough because the context already tells us what tea is replacing.

Because the sentence begins with a subordinate if-clause:

• Hvis vi løber tør for kaffe

and then moves to the main clause:

• vil vi drikke te i stedet

The comma marks the end of the subordinate clause and helps show the structure clearly.

So the sentence is divided like this:

• Hvis vi løber tør for kaffe,
• vil vi drikke te i stedet.

This is very common in Danish writing with clauses introduced by hvis.

Hvis is the normal Danish word for if in conditional sentences.

Examples:

• Hvis det regner, bliver vi hjemme. = If it rains, we stay home.
• Hvis du vil, kan vi gå nu. = If you want, we can go now.

So in your sentence, hvis introduces the condition: if we run out of coffee.

You may also meet om in some contexts involving whether / if, but that is different:

• Jeg ved ikke, om han kommer. = I don’t know whether he is coming.

So here hvis is the correct choice, not om.

• løber is present tense
• vil is a finite verb, also in the present form of the modal verb ville
• drikke is the infinitive

So the second clause is built like this:

• vil
  • drikke

This is the normal pattern after a modal verb in Danish:

• vil drikke = will drink
• kan drikke = can drink
• skal drikke = must / will drink

So drikke stays in the infinitive because it follows vil.

Yes. You can put the main clause first:

• Vi vil drikke te i stedet, hvis vi løber tør for kaffe.

That means the same thing.

The difference is mainly one of focus and style:

• Hvis vi løber tør for kaffe, vil vi drikke te i stedet.
  starts with the condition
• Vi vil drikke te i stedet, hvis vi løber tør for kaffe.
  starts with the result/plan

Notice that when the main clause comes first, the normal order is:

• Vi vil drikke ...

not

• Vil vi drikke ...

because now nothing else has taken the first position before the verb.

It usually sounds like a real, possible situation.

• Hvis vi løber tør for kaffe, vil vi drikke te i stedet.

This suggests: if that happens, this is the plan.

It is not especially distant or unreal. For a more clearly unreal or unlikely situation, Danish often uses other forms, for example with hvis vi løb tør ... ville vi ...

Compare:

• Hvis vi løber tør for kaffe, vil vi drikke te i stedet.
  = If we run out of coffee, we’ll drink tea instead.
  plausible / practical

• Hvis vi løb tør for kaffe, ville vi drikke te i stedet.
  = If we ran out of coffee, we would drink tea instead.
  more hypothetical

In natural speech, the sentence would often be said smoothly in two chunks:

• Hvis vi løber tør for kaffe,
• vil vi drikke te i stedet.

A speaker may slightly stress:

• tør in løber tør
• te
• i stedet

because those carry important meaning.

Also, in everyday speech, vil vi may sound quite closely connected, and i stedet is often pronounced as one rhythm unit.

So when practicing, it helps to think of the sentence in sense groups rather than word by word.