La festivalo havas ne nur muzikon, sed ankaŭ konkurson.

La is the definite article, meaning the. So la festivalo means the festival.

Esperanto has only one article: la. It does not have an indefinite article like English a/an. So:

• festivalo = a festival or just festival
• la festivalo = the festival

In Esperanto, nouns normally end in -o. So:

• festivalo = festival
• muziko = music
• konkurso = competition/contest

This -o ending is one of the most basic and regular parts of Esperanto grammar.

The -n ending marks the direct object. In this sentence, the festival has something, and the things it has are:

• muzikon
• konkurson

Since both are direct objects of havas, they take -n.

Compare:

• La festivalo havas muzikon. = The festival has music.
• La festivalo havas konkurson. = The festival has a competition.

Without the -n, the grammar would be wrong in standard Esperanto.

Havas means has. Esperanto often uses have in places where English might also say features, includes, or there is.

So La festivalo havas muzikon is literally The festival has music, but in natural English the idea may be closer to:

• the festival includes music
• the festival features music

Estas means is/are, so it would express a different structure.

This is the Esperanto pattern for not only ... but also ....

In your sentence:

• ne nur muzikon = not only music
• sed ankaŭ konkurson = but also a competition

So the full structure is:

• ne nur X, sed ankaŭ Y
• not only X, but also Y

It is a fixed and very common pattern.

In this pattern, both are normally used:

• sed = but
• ankaŭ = also

Together they make the full contrast:

• ne nur ..., sed ankaŭ ...
• not only ..., but also ...

If you removed one, the sentence would sound incomplete or less standard for this meaning.

Sometimes ankaŭ can move depending on what you want to emphasize, but in the expression ne nur ... sed ankaŭ ..., this placement is the normal and clearest one.

So:

• La festivalo havas ne nur muzikon, sed ankaŭ konkurson.

is the standard way to say it.

For learners, it is best to memorize ne nur ... sed ankaŭ ... as a set pattern.

Because the sentence is talking about music and a competition as types of things the festival has.

In Esperanto:

• muziko is often used as an uncountable noun, like English music
• konkurso here is a single competition/contest

If there were several competitions, you could say konkursojn instead.

Konkurso usually means competition or contest.

So in this sentence, it means the festival includes some kind of organized contest, not just music.

It is a noun, so it has the noun ending -o, and here it becomes konkurson because it is a direct object.

Yes, Esperanto word order is fairly flexible, but this version is the most straightforward and natural for learners:

• La festivalo havas ne nur muzikon, sed ankaŭ konkurson.

Because of the -n endings, Esperanto can often move parts around without losing the grammatical relationships. Still, with a structure like ne nur ... sed ankaŭ ..., it is usually best to keep the paired parts together clearly.

A couple of points may help:

• festivalo is pronounced roughly as written: fe-sti-VA-lo
• muzikon: mu-zi-KON
• konkurson: kon-KUR-son
• ankaŭ contains aŭ, which sounds somewhat like ow in cow

Esperanto pronunciation is very regular, so each letter is pronounced consistently.