Bare avledningen varer lenge nok, merker bursdagsbarnet ingenting.

Not in this sentence.

Here bare means something like as long as, provided that, or if only. It introduces a condition:

• Bare avledningen varer lenge nok ...
  = As long as the distraction lasts long enough ...

This is a very common thing for English speakers to trip over, because bare very often does mean only or just in other sentences.

For example:

• Jeg bare så på. = I was just watching.
• Bare du kommer, er jeg fornøyd. = As long as you come, I’m satisfied.

So you have to judge from context which meaning bare has.

Yes. A very straightforward alternative would be:

• Hvis avledningen varer lenge nok, merker bursdagsbarnet ingenting.

That means almost the same thing: If the distraction lasts long enough, the birthday child notices nothing.

The version with bare can sound a bit more like provided that / as long as. So the meaning is conditional, but with a slight nuance of that is the only requirement.

Because Norwegian main clauses follow the V2 rule: the finite verb normally comes in the second position.

Here, the whole first clause is placed first:

• Bare avledningen varer lenge nok, ...

After that comes the main clause, and in that main clause the finite verb must come before the subject:

• ... merker bursdagsbarnet ingenting.

So the pattern is:

1. first element: Bare avledningen varer lenge nok
2. finite verb: merker
3. subject: bursdagsbarnet

If you kept normal subject-verb order there, it would sound wrong in standard Norwegian.

Bursdagsbarnet is a compound noun:

• bursdag = birthday
• barn = child
• bursdagsbarnet = the birthday child

In practice, it means the person whose birthday it is. Even if the person is not literally a child, Norwegian sometimes still uses this word in a playful or affectionate way.

So depending on context, it could be understood as:

• the birthday child
• the birthday boy/girl
• the birthday person
• the celebrant

Grammatically, avledningen is the definite singular form:

• en avledning = an avledning
• avledningen = the avledning

In this sentence, it most naturally means the distraction or the diversion.

So:

• avledningen varer lenge nok
  = the distraction lasts long enough

The noun avledning can have other meanings in other contexts, but here distraction/diversion is the one that fits.

Lenge nok means long enough.

Norwegian usually puts nok after the adjective or adverb it modifies:

• stor nok = big enough
• gammel nok = old enough
• fort nok = fast enough
• lenge nok = long enough

So the order is the natural Norwegian order. English uses enough after the adjective/adverb too, so this part matches English fairly well.

Both are possible in many contexts.

• merker ingenting = notices nothing
• merker ikke noe = does not notice anything

In this sentence, ingenting is compact and very natural.

So:

• Bursdagsbarnet merker ingenting.
• Bursdagsbarnet merker ikke noe.

Both can work, though ingenting may feel slightly more direct and self-contained.

Yes. The first part functions as a conditional clause placed before the main clause, and a comma there is normal:

• Bare avledningen varer lenge nok, merker bursdagsbarnet ingenting.

This helps separate the condition from the result.

English often does the same:

• If the distraction lasts long enough, the birthday child notices nothing.

So the comma is not surprising here.

Yes. It is a complete sentence, and the structure is natural.

A useful way to read it is:

• Bare avledningen varer lenge nok = conditional part
• merker bursdagsbarnet ingenting = main statement

In more everyday Norwegian, many speakers might choose hvis instead of bare, but the sentence as written is still valid and understandable.