Buldreøkten begynner på buldresenteret.

Because Norwegian normally writes compound nouns as single words.

• buldre + økt → buldreøkt
• buldre + senter → buldresenter

This is much more consistent in Norwegian than in English. The last part is the main noun, so it controls the grammar:

• buldreøkt follows økt
• buldresenter follows senter

So if you can identify the last part of a compound, that often helps you understand how the whole word behaves.

In Norwegian, the definite article is usually attached to the end of the noun.

• buldreøkten = the bouldering session
• buldresenteret = the bouldering center

So instead of a separate word like English the, Norwegian often uses an ending:

• en økt = a session
• økten = the session
• et senter = a center
• senteret = the center

If there is an adjective, Norwegian often uses both a separate article and the ending:

• den lange buldreøkten = the long bouldering session

That depends on the gender of the noun.

• senter is a neuter noun, so the definite singular is senteret
• økt is commonly used with -en in Bokmål here, giving økten

A useful detail: økt is often treated as a feminine noun, so you may also see:

• ei buldreøkt
• buldreøkta

But in Bokmål, many speakers and writers also use:

• en buldreøkt
• buldreøkten

So buldreøkten is completely normal.

Begynner is the present tense of å begynne, which means to begin.

• å begynne = to begin
• begynner = begins / is beginning

In Norwegian, the present tense is also often used for scheduled future events, just like in English:

• Toget går klokka åtte = The train leaves at eight
• Buldreøkten begynner på buldresenteret can describe something happening now or something scheduled to start

So the form is present tense, but the time meaning depends on context.

Here på means something like at.

Norwegian often uses på for places such as schools, workplaces, venues, and activity locations:

• på skolen = at school
• på jobb = at work
• på treningssenteret = at the gym
• på buldresenteret = at the bouldering center

If you said i buldresenteret, that would sound more like inside the bouldering center physically. På is the more natural choice if you mean the place as a venue.

Yes, in Bokmål you often can.

Both of these can be correct:

• buldreøkten
• buldreøkta

That is because økt is a noun that can often appear with either form in Bokmål, depending on style and preference.

Very roughly:

• buldreøkta may feel a bit more clearly feminine
• buldreøkten may feel a bit more neutral or more typical in some written styles

Both are understandable and natural.

Mostly yes. The sentence follows a simple pattern:

• Buldreøkten = subject
• begynner = verb
• på buldresenteret = place expression

So it is basically:

Subject + Verb + Place

That said, Norwegian has a strong verb-second rule in main clauses. If you move another element to the front, the verb still stays in second position:

• På buldresenteret begynner buldreøkten.

That is grammatical, although the original sentence is more neutral and natural in many contexts.

The letter ø does not have an exact English equivalent.

A rough guide:

• shape your lips somewhat as if you were saying o
• but try to place your tongue more like for e or i

You hear ø in both:

• buldreøkten
• buldresenteret

It is the same letter as in words like:

• øl
• søster
• høre

If you already know French or German, it is somewhat similar to the vowel in French peu or German schön, though not always exactly the same.

Yes. Starter would sound natural here too.

• Buldreøkten begynner på buldresenteret.
• Buldreøkten starter på buldresenteret.

In many everyday contexts, they mean almost the same thing.

A small difference in feel:

• begynner = begins
• starter = starts

But in a sentence like this, either one works well.

Yes, it is natural.

It sounds like a normal sentence about an activity session taking place at a bouldering gym or center. The vocabulary is modern and straightforward, and the grammar is standard.

The only thing that can vary is personal preference in wording, for example:

• buldreøkta instead of buldreøkten
• starter instead of begynner

But the original sentence is perfectly good Norwegian.