На этой поляне летом много комаров, поэтому мы не сидим там долго.

Russian usually uses на with open spaces, surfaces, and many outdoor locations, while в is more common for enclosed spaces.

So:

• на поляне = in/on the clearing
• в комнате = in the room

A поляна is an open clearing, so на sounds natural.

Also, after на in a location meaning, Russian uses the prepositional case:

• эта поляна → на этой поляне

So на этой поляне means on/in this clearing.

Because the phrase is in the prepositional case, singular, feminine.

The base form is:

• эта поляна = this clearing

After на meaning location, both the adjective/pronoun and the noun must match in the prepositional case:

• эта → этой
• поляна → поляне

So:

• на этой поляне = in this clearing / on this clearing

This is normal adjective-noun agreement in Russian.

Russian often uses the instrumental case by itself for seasons and some time expressions.

So:

• лето = summer
• летом = in summer / during the summer

This is a very common pattern:

• зимой = in winter
• весной = in spring
• осенью = in autumn

You can think of летом as a set time expression meaning during the summer.

After много (many / a lot of), Russian normally uses the genitive plural.

So:

• комар = mosquito
• комары = mosquitoes (nominative plural)
• комаров = of mosquitoes / mosquitoes after quantity words

Therefore:

• много комаров = many mosquitoes / a lot of mosquitoes

This happens with many quantity words:

• много людей = many people
• мало времени = little time
• несколько книг = several books

Because in the present tense, Russian usually omits есть when it means is/are in simple statements.

So the sentence literally looks like:

• On this clearing in summer many mosquitoes

But the natural English meaning is:

• There are many mosquitoes in this clearing in summer

Russian often leaves out the present-tense to be:

• Он студент = He is a student
• Здесь тепло = It is warm here
• На этой поляне много комаров = There are many mosquitoes in this clearing

Поэтому means therefore, so, or that’s why.

It connects the first idea to the result:

• На этой поляне летом много комаров, поэтому...
• There are many mosquitoes in this clearing in summer, so...

It introduces a consequence:

• cause: many mosquitoes
• result: we do not sit there long

It is a very common linking word in Russian.

Russian сидеть literally means to sit, but in many contexts it also means to sit/stay somewhere for some time, especially when people are resting, hanging out, or remaining seated.

So here:

• мы не сидим там долго

can sound more natural in English as:

• we don’t stay there long
• we don’t sit there for long

Russian often uses сидеть where English might prefer stay.

The present tense here expresses a general/habitual fact, not something happening only right now.

So the sentence means something like:

• We don’t stay there long
• We don’t usually sit there for long

This is not about one specific moment. It is a regular pattern: because there are many mosquitoes there in summer, we do not remain there long.

Сидеть is an imperfective verb, and that fits because the sentence describes an ongoing or repeated situation, not a single completed action.

Imperfective is used for:

• habits
• general truths
• ongoing states
• repeated actions

Here it is a habitual/general statement, so сидим is exactly what you would expect.

A perfective verb would suggest a single completed action and would not fit as naturally here.

Because Russian, like English, often repeats a place with a word like там (there) to sound natural.

The first clause introduces the location:

• На этой поляне...

Then the second clause refers back to it:

• ...поэтому мы не сидим там долго

This is similar to English:

• There are lots of mosquitoes in this clearing in summer, so we don’t stay there long.

The там is not strictly necessary, but it sounds natural and helps the flow.

Долго means for a long time or long in the sense of duration.

So:

• не сидим там долго = we don’t sit/stay there long

Compare:

• долгий = long (adjective)
• долго = long / for a long time (adverb)

Examples:

• Он долго ждал. = He waited a long time.
• Мы там долго не были. = We had not been there for a long time.

Yes. Russian word order is more flexible than English word order, although different orders can change emphasis.

The given sentence is natural:

• На этой поляне летом много комаров, поэтому мы не сидим там долго.

But other versions are possible, for example:

• Летом на этой поляне много комаров...
• ...поэтому долго мы там не сидим.
• ...поэтому мы там долго не сидим.

These all mean roughly the same thing, but the emphasis shifts:

• летом first emphasizes in summer
• долго earlier can emphasize not for long
• там earlier can emphasize there

The original version is neutral and natural.

You could translate it literally word-for-word for study purposes, but it would not sound natural in English.

A natural English translation would be:

• There are many mosquitoes in this clearing in summer.
• This clearing has a lot of mosquitoes in summer.

So for understanding the Russian structure, the literal gloss is useful. But for normal English, you would usually add there are.

Here it is genitive plural, required by много.

The base forms are:

• комар = mosquito
• комары = mosquitoes
• комаров = mosquitoes in the genitive plural

Animacy is important in some Russian forms, especially the accusative plural, but in this sentence the form is used because of the quantity word много, not because of animacy alone.

So the key rule here is:

• много + genitive plural

Yes, absolutely.

Both are natural:

• На этой поляне летом много комаров
• Летом на этой поляне много комаров

The difference is mainly emphasis:

• На этой поляне... puts the location first
• Летом... puts the time first

Russian often moves time and place expressions around depending on what the speaker wants to highlight.

In meaning, it can be either, depending on the tone.

• In a more formal or careful translation: therefore
• In everyday English: so or that’s why

In this sentence, so is probably the most natural English equivalent:

• There are lots of mosquitoes there in summer, so we don’t stay there long.

So поэтому is very common and works in both everyday and more formal Russian.