Learn Hardcore Norwegian: Unnskyld, jeg kommer for sent.

Unnskyld – literally excuse (imperative form of å unnskylde = to excuse). Used like sorry or excuse me.
jeg – I.
kommer – come / am coming.
for – here it means too, as in too late, not for like in English for you.
sent – adverb form of sen (late), so sent = late(ly) / late as an adverb.

So the literal idea is: Excuse (me), I come too late.

Why do Norwegians say jeg kommer for sent (I come too late) instead of something like I am late?

Norwegian often uses the verb komme (to come) to talk about arriving late.
The set expression is å komme for sent = to be late (for something).
So jeg kommer for sent is the natural idiomatic way to say I’m late / I’m arriving late.
You can also use å være sen (to be late) in other structures, but for apologizing about arriving late, komme for sent is very common and very natural.

Can I say instead of ?