Learn Portuguese (Portugal): Eu moro neste apartamento.

The word neste is a contraction (a combination) of the preposition em (which means "in", "on", or "at") and the demonstrative word este (which means "this"). Instead of saying em este, Portuguese naturally merges them together into neste to mean "in this".

Why do we use neste and not nesta?

In Portuguese, pointing words like "this" have to match the gender of the noun they describe. Because apartamento (flat) is a masculine word, we must use the masculine form este. When combined with em, it becomes neste. If you were talking about a feminine noun, like casa (house), you would use nesta instead.

Can I use the verb viver instead of morar to say "I live" here?

Yes, you can! Both morar and viver can translate to "to live" in English. The verb morar specifically means to reside somewhere physically (like a flat, street, or city), making it perfect for this sentence. viver is also very commonly used for residing, but it has a broader meaning of "being alive" or "experiencing life" as well.

Do I have to include Eu at the beginning of the sentence?