Du overdriver bestemt ikke, hvis du siger, at køen ved stationen var lang i morges.

This is the main clause, and it means something like You are definitely not exaggerating.

A few useful points:

• du = you
• overdriver = exaggerate / are exaggerating
• bestemt ikke = definitely not / certainly not

In Danish main clauses, the finite verb usually comes in second position, so overdriver comes right after Du.

Bestemt ikke is an emphatic way of saying not at all, certainly not, or definitely not.

So:

• Du overdriver ikke = You are not exaggerating
• Du overdriver bestemt ikke = You are definitely not exaggerating

Here bestemt strengthens the negation. It does not mean in a determined way here.

Because bestemt is modifying the negation as a whole, and bestemt ikke is a natural fixed combination in Danish.

So the normal wording is:

• Du overdriver bestemt ikke

If you said ikke bestemt, it would sound unnatural in this sentence.

Because there are two clauses:

1. Du overdriver bestemt ikke
2. hvis du siger, at køen ved stationen var lang i morges

Each clause needs its own subject, so du appears again in the hvis clause.

This is very normal in Danish, just as in English:

• You are not exaggerating if you say...

Hvis means if.

It introduces a conditional clause:

• hvis du siger = if you say

So the sentence means that if you say the queue at the station was long this morning, that is not an exaggeration.

Here at means that and introduces a content clause:

• du siger, at køen ... var lang = you say that the queue ... was long

In English, that is often optional:

• you say that the queue was long
• you say the queue was long

In Danish, at is very commonly used in this kind of sentence.

Køen is the definite form of kø:

• en kø = a queue
• køen = the queue

Danish usually adds the definite article as an ending:

• kø → køen
• station → stationen

So køen ved stationen means the queue at/by the station.

Ved usually means by, near, or sometimes at.

So ved stationen means:

• by the station
• at the station
• near the station

In this sentence, English would probably most naturally say at the station, but Danish uses ved very naturally here.

Stationen is the definite form of station:

• en station = a station
• stationen = the station

So ved stationen means at/by the station, referring to a specific station that is understood from context.

Because lang is a predicate adjective here.

After var (was), Danish uses the basic adjective form:

• Køen var lang = The queue was long

You do not use the definite ending here, because lang is not directly placed before a noun. Compare:

• en lang kø = a long queue
• den lange kø = the long queue
• køen var lang = the queue was long

Yes. Danish uses lang very naturally for a queue, line, wait, road, speech, and many other things that extend in time or space.

So:

• Køen var lang = The queue was long

This works just like English.

Because Danish word order changes in subordinate clauses.

In a main clause, Danish usually has verb second:

• Du overdriver ikke

But in a subordinate clause introduced by at, hvis, fordi, etc., the finite verb does not have to stay in second position. So you get:

• at køen ved stationen var lang
• hvis du siger ...

That is normal Danish subordinate-clause word order.

This is a very common confusion.

• i morges = this morning
• i morgen = tomorrow

So in this sentence:

• var lang i morges = was long this morning

They look similar, but they mean very different things.

The commas separate the different clauses:

• Du overdriver bestemt ikke
• hvis du siger
• at køen ved stationen var lang i morges

So the commas help show the structure of the sentence.

Very roughly:

• main statement
• condition
• embedded statement

This makes the sentence easier to read.

Yes, absolutely.

Because bestemt ikke is emphatic, several English versions work well:

• You are definitely not exaggerating if you say...
• You are certainly not exaggerating if you say...
• You are by no means exaggerating if you say...

The exact English wording can vary, but the Danish grammar stays the same.

Yes.

• overdriver = present tense
• var = past tense

That is completely normal, because they belong to different parts of the sentence:

• Du overdriver bestemt ikke = present-time statement about what you are doing now
• at køen ... var lang i morges = past event, because it refers to this morning

So the sentence mixes present and past naturally.

Yes. That would still be correct.

• Du overdriver ikke, hvis du siger... = You are not exaggerating if you say...
• Du overdriver bestemt ikke, hvis du siger... = You are definitely not exaggerating if you say...

Adding bestemt just makes the statement stronger and more emphatic.