Az uszoda ma nyitva van.

Hungarian has two forms of the definite article:

• a before a consonant
• az before a vowel

So because uszoda starts with the vowel u, you say az uszoda.

This is a bit like English a/an, but the meaning is the, not a/an.

Uszoda usually means swimming pool in the sense of the facility/place, not just the water itself.

So Az uszoda ma nyitva van means the swimming-pool facility is open today.

A useful contrast:

• uszoda = the swimming-pool building/facility
• medence = the actual pool basin

A few important pronunciation points:

• sz is pronounced like English s
• Hungarian s on its own is pronounced like English sh
• ny is a soft sound, similar to the ny in canyon
• stress usually falls on the first syllable of each word

So:

• uszoda sounds roughly like OO-so-daw
• nyitva sounds roughly like NYIT-vaw

Also, Hungarian a is not exactly English a; it is closer to the vowel in British hot.

Nyitva comes from the verb nyit(ni), meaning to open.

In this sentence, nyitva describes a state: something is in an open condition.

So:

• nyitva van = is open
• zárva van = is closed

This -va/-ve form is very common in expressions about result or state.

That is a very common question.

In Hungarian, the present-tense to be is often omitted in the third person singular:

• Az uszoda nagy. = The swimming pool is big.

But with some kinds of predicates, especially states and location-like expressions, van is normally kept:

• Az uszoda nyitva van. = The swimming pool is open.
• Itthon van. = He/she is at home.
• Készen van. = It is ready.

So in nyitva van, the van is completely normal and expected.

Usually, for shops, offices, pools, and opening hours, nyitva van is the most natural choice.

• Az uszoda nyitva van. = The pool is open.

Nyitott does exist, but it is used differently and is often less natural in this kind of sentence.

Examples:

• nyitott ajtó = an open door
• nyitott kérdés = an open question
• nyitott ember = an open-minded person

So for business-hours type meanings, stick with nyitva van.

Yes, Hungarian word order is flexible, and it often shows what is being emphasized.

The sentence Az uszoda ma nyitva van is a natural, neutral way to say it.

Other possibilities are also possible, but they can sound a little different:

• Ma nyitva van az uszoda.
  This can put a bit more attention on today.

• Az uszoda ma van nyitva.
  This gives stronger emphasis to today, often with a contrast such as today, not tomorrow.

• Az uszoda nyitva van ma.
  Possible, but less neutral; it can sound like today is added afterward.

So the original sentence is a very normal word order.

Yes, az uszoda normally refers to a specific, known swimming pool: for example, the local pool, the one you have already been talking about, or the one both speakers know.

In a normal sentence, you usually keep the article:

• Az uszoda ma nyitva van.

Leaving it out:

• Uszoda ma nyitva van

would sound unnatural in ordinary speech, though it might appear in a headline, note, or very telegraphic style.

The most direct negative is:

• Az uszoda ma nincs nyitva. = The swimming pool is not open today.

Another very common way is:

• Az uszoda ma zárva van. = The swimming pool is closed today.

These are close in meaning, but not identical:

• nincs nyitva = is not open
• zárva van = is closed

Both are natural.

By itself, ma means today, so the sentence is about the pool’s status on this day.

It does not automatically mean right this moment. It usually means something like:

• the pool is open today
• today is one of its open days
• today it is operating / accessible

If you wanted to stress right now, Hungarian would usually add something else, depending on context.