A főnök üzleti találkozóra megy a szállodába.

A is the definite article in Hungarian, equivalent to “the”.
Hungarian normally repeats the article in front of each definite noun phrase, so you get A főnök … a szállodába = “The boss … to the hotel.”
Before words starting with a vowel sound, a turns into az (e.g. az orvos = “the doctor”), but here both főnök and szálloda start with consonants, so a is used.

Hungarian usually does not use separate prepositions like “to” for direction; it uses case endings on the noun instead.
The ending -ba on szállodába means “into / to (the inside of)”, so szálloda (hotel) + -ba → “into the hotel / to the hotel.”
So a szállodába literally means “to-into the hotel,” and that replaces “to the hotel” in English.

Both endings express direction, but they’re used differently:

• -ba / -be = “into” a place (movement into an interior):
  
  • szálloda → szállodába = (to) into the hotel.
• -ra / -re = originally “onto”, but it’s also used for events/occasions:
  
  • találkozó → találkozóra = to/for a meeting.

So üzleti találkozóra megy is “(he) goes to a business meeting,” while a szállodába megy is “(he) goes into the hotel.”

Üzlet means “shop” or “business” as a noun.
The suffix -i often turns a noun into an adjective with the meaning “related to / of / about X.”
So üzleti ≈ “business-related” or simply “business” as an adjective, and üzleti találkozó is literally “business meeting.”
Without -i, üzlet találkozó would be wrong; you need üzleti to modify találkozó correctly.

The base noun is találkozó = “meeting.”
When you add -ra/-re to a noun, you usually get “to / onto / for (that)” in a directional sense.
So találkozóra means “to a meeting / for a meeting.”
In this sentence, üzleti találkozóra megy = “(he) is going to a business meeting.”

Megy is the 3rd person singular present tense of the verb menni = “to go.”
Hungarian doesn’t have a separate present continuous (“is going”) form; simple present covers both “goes” and “is going.”
So A főnök … megy can be translated as either “The boss goes …” or “The boss is going …,” depending on context.
A common variant is elmegy (“go(es) away / off”), but here megy alone is perfectly natural.

In Hungarian, present-tense action verbs (like megy) don’t use an extra “to be” verb.
The single word megy already expresses “is going / goes.”
You only see a separate form of “to be” (e.g. van) in certain structures, such as “He is a boss” – Ő főnök (and even there, van is usually omitted in the 3rd person present).
For progressive meaning (“is going”), context plus the present tense verb is enough.

Yes, Egy üzleti találkozóra megy a szállodába is grammatically correct.
Egy is the indefinite article (“a / an”).
Hungarian often omits the indefinite article with certain kinds of events and roles (e.g. meetings, lessons, jobs) when they’re not being emphasized.
Adding egy can sound a bit more like “to a (certain) business meeting,” while leaving it out is more neutral and generic.

The neutral Hungarian word order is often Subject – (other info) – Verb – (destination) or simply Subject – Verb – Other, but in practice it’s quite flexible.
Here, A főnök üzleti találkozóra megy a szállodába is a normal, neutral sentence:

• A főnök = subject
• üzleti találkozóra = purpose
• megy = verb
• a szállodába = final destination.

You could move parts around for emphasis, but this order sounds natural and unmarked.

You add a possessive ending to főnök:

• főnököm = my boss (főnök + -öm).

So the sentence is:
A főnököm üzleti találkozóra megy a szállodába.
Literally: “The my-boss business-meeting-to goes the hotel-into.”

You pluralize both the noun and the verb:

• főnök → főnökök (bosses)
• megy → mennek (they go / are going)

So the full sentence is:
A főnökök üzleti találkozóra mennek a szállodába.

In Hungarian, the acute accent (á, é, í, ó, ú, ő, ű) marks long vowels, not stress.

• főnök: ő is a long front rounded vowel; it’s held longer than ö.
• szállodába: á is a long a; again, held longer than a.

Word stress is always on the first syllable in Hungarian, so: FŐ-nök, SZÁL-lo-da-ba.