Эта порода собак обычно любит бегать, поэтому мы долго гуляем вечером.

Because порода is a feminine singular noun, and эта is the feminine singular form of this.

• masculine: этот
• feminine: эта
• neuter: это
• plural: эти

So:

• эта порода = this breed

Both words are in the nominative singular, because эта порода собак is the subject of the sentence.

Because after a noun like порода meaning breed/type/kind, Russian usually puts the second noun in the genitive.

So:

• порода собак = a breed of dogs
• вид птиц = a species of birds
• группа студентов = a group of students

Here собак is the genitive plural of собаки.

This structure is very common in Russian:

• main noun + genitive noun

So порода собак literally works like breed of dogs.

Because the real grammatical subject is порода, not собак.

So the verb agrees with порода:

• порода ... любит
• not порода ... любят

Even though the meaning involves dogs, grammatically the sentence is saying something like:

• This breed of dogs usually likes to run

Russian verb agreement follows the main noun, not the noun inside the of dogs part.

Because бегать is the normal verb for running as a general activity, especially something habitual or repeated.

Here the sentence is about what this breed usually likes to do in general, so бегать fits perfectly.

Very roughly:

• бегать = to run around / to run regularly / to run as an activity
• бежать = to be running in one direction right now / to run somewhere specific

Compare:

• Собака любит бегать. = The dog likes running.
• Собака бежит домой. = The dog is running home.

So after любит, Russian often uses an infinitive that expresses a general activity, and бегать is the natural choice here.

Because обычно means usually, and it commonly goes before the verb it modifies.

So:

• обычно любит бегать = usually likes to run

This is a very normal word order in Russian.

You can sometimes move обычно for emphasis, for example:

• Эта порода собак любит обычно бегать
• Обычно эта порода собак любит бегать

But the original order sounds natural and neutral.

Поэтому means therefore / so / that’s why. It connects the second clause to the first one as a result.

Structure:

• clause 1: this breed usually likes running
• поэтому
• clause 2: we walk for a long time in the evening

So it shows cause → result.

It is not the same as потому что:

• поэтому = therefore / so
• потому что = because

Compare:

• Собака любит бегать, поэтому мы долго гуляем.
  The dog likes to run, so we walk for a long time.

• Мы долго гуляем, потому что собака любит бегать.
  We walk for a long time because the dog likes to run.

Because Russian normally separates clauses in a compound sentence with a comma.

Here there are two clauses:

1. Эта порода собак обычно любит бегать
2. поэтому мы долго гуляем вечером

Since they are connected but still separate clauses, the comma is required.

Russian punctuation is often stricter than English in this kind of sentence.

Because гулять means to walk / to go for a walk / to spend time walking for pleasure.

That matches the idea here: the people are taking a long walk with the dog in the evening.

Compare:

• гулять = to stroll, walk for leisure, go out for a walk
• идти = to be going, to walk in one direction right now
• ходить = to go/walk habitually or back and forth

So:

• мы долго гуляем вечером = we spend a long time walking in the evening

This sounds much more natural than идём in this context.

Долго means for a long time. It modifies the verb гуляем, so it is an adverb.

• долго гуляем = we walk for a long time

A native English speaker may expect something like long, but Russian uses the adverb долго with verbs.

Compare:

• долгая прогулка = a long walk
  
  • adjective + noun
• долго гуляем = we walk for a long time
  
  • adverb + verb

So долго describes the duration of the action.

Because Russian often uses certain time words in the instrumental case to mean in the morning / in the evening / during the night, without a preposition.

Here:

• вечер = evening
• вечером = in the evening

Other common examples:

• утром = in the morning
• днём = in the daytime
• ночью = at night

So вечером is just a standard time expression.

Yes to both.

Russian word order is flexible, so you can move parts of the sentence to change emphasis. For example:

• Вечером мы долго гуляем
• Мы вечером долго гуляем
• Обычно эта порода собак любит бегать, поэтому вечером мы долго гуляем

These all keep the basic meaning, but the emphasis shifts a little.

Also, мы can be omitted if the subject is already clear:

• Эта порода собак обычно любит бегать, поэтому долго гуляем вечером.

That is possible because гуляем already shows we through the verb ending.

However, keeping мы is completely natural and often clearer, especially for learners or when you want to state the subject explicitly.