Learn Swedish: Älskaren lär vilja ha pengarna från arvet. - The lover reportedly wants the money from the inheritance.

It can, but here it acts as a special modal verb. When used with another verb in the infinitive (like vilja), lär means "reportedly", "is said to", or "is highly likely to". Here, it shows that the speaker heard this information from someone else, hence "reportedly".

Why do we need both vilja and ha here? Can't we just say lär vilja pengarna?

No, in Swedish you cannot use vilja directly with a noun object like you do in English ("wants the money"). You have to say "wants to have" the object, which is vilja ha. Since lär is a modal verb, the next verbs must be in their infinitive forms (vilja and ha).

Why is pengarna plural when "money" is a singular concept in English?

In Swedish, the word for money (pengar) is a plural noun. To say "the money" (definite form), you use the definite plural ending -na, creating pengarna.

How is the definite form älskaren built?

The base word for a lover is en älskare. For "en" words that end in -are, you simply add -n to create the definite singular form. So älskare becomes älskaren.