Jeg kan ikke bevæge min arm, fordi den gør ondt.

In a normal main clause, Danish usually puts the finite verb in second position. So you get:

Jeg kan ikke bevæge min arm.

Here, kan comes before ikke.

You often see ikke kan in a subordinate clause, for example:

... fordi jeg ikke kan bevæge min arm.

So the difference is mainly about sentence structure, not meaning.

Because after a modal verb like kan, Danish normally uses the infinitive without at.

So:

• jeg kan bevæge
• jeg vil bevæge
• jeg skal bevæge

But with many other verbs, you do use at:

• jeg prøver at bevæge min arm

This is similar to English, where you say I can move, not I can to move.

Kan here means am able to or can.

So Jeg kan ikke bevæge min arm means that the speaker is unable to move the arm.

Depending on context, kan can also express:

• ability
• possibility
• permission

But in this sentence, it is clearly about ability.

Because the sentence is talking about one arm, and arm is a common-gender singular noun.

So:

• min arm = my arm
• armen = the arm
• mine arme = my arms

Danish usually uses the possessive here, just like English does: my arm.

Because arm is a common-gender noun, and common-gender nouns take den.

• en arm → den
• et ben → det

So in this sentence, den refers back to min arm.

Gør ondt is the normal Danish expression for hurts or is painful.

Literally, it is something like does pain, but you should learn it as a fixed expression:

• Det gør ondt = It hurts
• Min arm gør ondt = My arm hurts

Danish often uses this expression instead of a single direct equivalent of English hurt.

Because ondt is the form used in this fixed expression: gøre ondt.

You do not normally say gør ond here.

Also, ond as an adjective often means evil or bad in other contexts, while ondt in gøre ondt is part of the idiomatic expression meaning to hurt.

So it is best to memorize:

gøre ondt = to hurt

In standard written Danish, a comma is normally used before a subordinate clause, and fordi introduces one.

So:

Jeg kan ikke bevæge min arm, fordi den gør ondt.

This is standard Danish punctuation.

In English, comma use before because is more variable, but in Danish the comma is much more regular in this kind of sentence.

Because fordi starts a subordinate clause, and subordinate clauses do not use normal main-clause word order.

Compare:

• Main clause: Den gør ondt
• Subordinate clause: ... fordi den gør ondt

The subject den comes before the verb gør.

This is an important difference in Danish:

• main clause: verb typically in second position
• subordinate clause: subject usually comes before the finite verb

Yes, sometimes, but bevæge is a more general and natural choice here.

• bevæge = move, move around, cause to move
• flytte = move something from one place to another, or shift it

If you are talking about being unable to move your arm because of pain, bevæge min arm sounds very natural.

Flytte min arm is possible in some contexts, but it can sound more like shift my arm’s position rather than simply move my arm.

Yes.

• bevæge min arm = move my arm
• røre min arm = touch my arm or sometimes move my arm slightly, depending on context

A learner should be careful, because røre often means touch, not just move.

So if the intended meaning is that the arm cannot physically be moved, bevæge is the safer choice.

A rough guide is something like beh-VEH-yuh or beh-VAI-yuh, but Danish pronunciation varies and is hard to represent with English spelling.

A few helpful points:

• be- is usually light and unstressed
• the stress is on -væ-
• the final -ge is not pronounced like English g

If possible, the best approach is to listen to native audio and repeat it several times, because Danish pronunciation is often less phonetic than the spelling suggests.

Very roughly:

• gør sounds somewhat like guh/r with a rounded vowel that English does not really have
• ondt sounds roughly like ohnt, but the exact vowel and consonants are very Danish

A few notes:

• gør contains ø, which is a rounded front vowel
• ondt is pronounced more tightly than an English speaker might expect
• the written form does not map neatly onto English sounds

Again, listening to native pronunciation is much more useful than relying only on English-style spelling.

In this sentence, den clearly refers to min arm.

That is because:

• arm is singular
• arm is common gender
• it is the most natural noun for den to refer back to

So the meaning is: the arm hurts, and that is why the speaker cannot move it.

Yes, it sounds natural.

Both parts are very normal:

• Jeg kan ikke bevæge min arm
• fordi den gør ondt

A Danish speaker might also say similar things like:

• Jeg kan ikke bevæge armen
• Jeg kan ikke løfte min arm
• Min arm gør for ondt til, at jeg kan bevæge den

But your original sentence is completely normal and idiomatic.