gōuhuǒ yíhuìr hěn dà, yíhuìr hěn xiǎo.

In Mandarin, adjectives can act as the predicate by themselves, so you do not need a separate verb like is.

So:

• 篝火很大 = The bonfire is big
• 篝火很小 = The bonfire is small

This is very normal in Chinese. English usually needs to be, but Mandarin often does not.

Not always. In sentences like this, 很 often does not strongly mean very. It often works more like a natural link before an adjective.

So 很大 and 很小 here are often best understood as:

• big
• small

rather than:

• very big
• very small

If you remove 很, the sentence can sound more contrastive or less neutral in many situations.

Here, 一会儿……一会儿…… means something like:

• one moment... and the next...
• now... now...
• at one moment... at another...

So the sentence describes something that keeps changing:

• The bonfire is big one moment, small the next.

This pattern shows alternation over time.

No. 一会儿 has more than one common use.

By itself, it can mean:

• a little while
• in a moment
• for a while

But in the paired pattern 一会儿……一会儿……, it means:

• one moment... another moment...
• now... then...

So in this sentence, it is not talking about the future. It is describing repeated change.

This is because of the tone change rule for 一.

Normally, 一 is first tone: yī.
But before a fourth-tone syllable, it changes to second tone: yí.

Since 会 is fourth tone (huì), 一会儿 is pronounced:

• yíhuìr

This is a very common tone sandhi rule.

The 儿 here is an erhua ending, meaning the syllable gets an r-colored sound.

So 一会儿 is pronounced roughly like:

• yíhuìr

not as two fully separate words like huì + ér.

Depending on accent and speaking style, the r sound may be stronger or lighter. In standard Mandarin, this kind of pronunciation is very common.

It does not need to be repeated. Once the topic or subject is clear, Mandarin often leaves it out in the next clause.

So:

• 篝火一会儿很大，一会儿很小

is understood as:

• 篝火一会儿很大，篝火一会儿很小

But repeating 篝火 would sound less natural here. Chinese often avoids unnecessary repetition when the meaning is already clear.

Not necessarily just physical size. With fire, 大 and 小 often describe how strong, high, or intense the fire is.

So here:

• 很大 can mean the fire is strong / high / blazing
• 很小 can mean the fire is weak / low

English might translate this more naturally as something like:

• The bonfire flares up and dies down.
• The bonfire is big one moment and small the next.

Yes, but it changes the feel.

• 篝火一会儿大，一会儿小 is possible.
• 篝火一会儿很大，一会儿很小 sounds more natural and smoother in ordinary description.

Using 很 before an adjective is very common in simple descriptive sentences. Without it, the sentence may sound more terse, literary, or contrastive depending on context.

No. They express different ideas.

• 一会儿……一会儿…… = alternation over time
  one moment..., the next...
• 一边……一边…… = two actions happening at the same time
  while... / at the same time...

So this sentence means the bonfire changes back and forth over time, not that two things are happening simultaneously.

The comma separates the two parallel parts of the sentence:

• 一会儿很大
• 一会儿很小

It helps show the rhythm and the contrast between the two states. Chinese punctuation is important for making this kind of repeated pattern easy to read.

Yes, very much so. 一会儿……一会儿…… is a common everyday structure for things that keep changing.

You can use it with many subjects, for example:

• 天气一会儿热，一会儿冷。
  The weather is hot one moment and cold the next.

• 他一会儿高兴，一会儿生气。
  He is happy one moment and angry the next.

So in your sentence, it naturally shows that the bonfire is flickering or changing in intensity.