Jeg har kun én bog i min taske.

Because Danish uses have for possession, just like English:

• Jeg har en bog = I have a book

So har is the present tense of at have (to have).

You use er for being, identity, location in some cases, etc., but not for owning or possessing something.

Yes, you can often write en. The accent in én is used to show that it means one specifically and is being stressed.

So:

• en bog = a book / one book in a neutral way
• én bog = one book with emphasis, often contrasting with a larger number

In this sentence, kun én bog strongly highlights only one book, so the accent makes that clearer.

Because bog is a common gender noun in Danish, and common gender nouns take en in the singular indefinite form.

• en/én bog = a/one book

If a noun were neuter, it would take et instead.

So this is a gender issue:

• en bog
• not et bog

Because bog here is indefinite singular: one book / a book.

• bog = book
• bogen = the book

Since the sentence says only one book, you are talking about the quantity, not a specific already-identified book. That is why Danish uses bog, not bogen.

In standard Danish, a possessive usually comes before the noun, and the noun stays in its indefinite form:

• min taske = my bag

So you do not normally say:

• min tasken ✘

That is because the possessive already makes the noun definite in meaning, so Danish does not add the definite ending here.

tasken min can occur in certain contexts, especially for emphasis or in speech, but min taske is the normal basic form learners should use.

Because taske is a common gender noun, and the possessive must match that.

• min
  • common gender singular noun
• mit
  • neuter singular noun
• mine
  • plural

So:

• min taske = my bag
• but for a neuter noun: mit hus = my house

Kun means only.

So:

• Jeg har kun én bog = I have only one book

It limits the quantity. The important idea is that the speaker has no more than one book in the bag.

Because kun is modifying the quantity phrase én bog.

In this sentence:

• Jeg = subject
• har = finite verb
• kun én bog = object phrase, with kun focusing on one book
• i min taske = prepositional phrase

So the structure is natural Danish word order:

• Jeg har kun én bog i min taske.

You would not normally say:

• Jeg kun har ... ✘

In a normal main clause, the finite verb comes early, and kun comes after it here.

Sometimes, but kun is the safer and more precise choice here.

• kun = only
• bare = often just / simply / only, depending on context

In a sentence about quantity, kun sounds very natural:

• Jeg har kun én bog i min taske.

Using bare is possible in some situations, especially in speech, but it can sound slightly different in nuance. For learners, use kun when you clearly mean only in a factual sense.

It literally means in my bag.

• i = in
• min = my
• taske = bag

So i min taske is a prepositional phrase telling you where the book is.

Without kun, the sentence would simply mean:

• Jeg har én bog i min taske. = I have one book in my bag.

That states the fact.
With kun, it adds the idea of limitation:

• Jeg har kun én bog i min taske. = I have only one book in my bag.

So kun is important if you want to stress that the number is small or limited.

In careful speech, jeg is often pronounced something like yai or yaiy, though exact pronunciation varies a lot by speaker and region.

In everyday spoken Danish, it is often reduced, and learners may hear something closer to:

• ya
• yai

This is normal. Danish pronunciation is often much more reduced than the spelling suggests, so jeg is a word worth listening to many times.