В конце августа мы обычно покупаем тетради и готовимся к осени.

This is a fixed and very common pattern:

• в конце = at the end
• августа = of August

The grammar works like this:

• в
  • конце uses the prepositional case here, because it means in/at the end
• конец then takes the genitive for the thing whose end you mean:
  • конец дня = the end of the day
  • конец недели = the end of the week
  • конец августа = the end of August

So в конце августа literally means at the end of August.

Because after конец Russian normally uses the genitive:

• конец чего? = the end of what?

So:

• конец августа = the end of August

You would use августе in a different structure, for example:

• в августе = in August

Compare:

• в августе = in August
• в конце августа = at the end of August

So both are correct, but they belong to different constructions.

In Russian, the present tense of imperfective verbs is often used for habitual or repeated actions.

So:

• мы обычно покупаем = we usually buy
• мы обычно готовимся = we usually get ready / prepare

This is exactly how Russian normally expresses habits or routines.

The word обычно = usually makes that especially clear.

So the sentence is not about what is happening right this second. It is about a customary action.

Here тетради is the accusative plural of тетрадь.

Because тетрадь means notebook / exercise book, and in this sentence it is the direct object of покупаем:

• покупаем что? = we buy what?
• тетради

For inanimate plural nouns, the accusative plural is usually the same as the nominative plural.

So:

• nominative plural: тетради
• accusative plural: тетради

That is why the form stays тетради here.

The dictionary form is тетрадь.

It is:

• feminine
• singular
• ending in -ь

Its plural is:

• тетради

This is a useful noun to remember because English speakers often learn it early in school-related vocabulary.

Because the verb is готовиться, not готовить.

These are different verbs:

• готовить = to prepare something, to cook
• готовиться = to get ready, to prepare oneself

So:

• мы готовим ужин = we are preparing dinner
• мы готовимся к осени = we are getting ready for autumn

The -ся makes the verb reflexive, and in this case the meaning is closer to get ready / prepare oneself.

The preposition к takes the dative case.

Here it means something like:

• toward
• for
• in preparation for

So:

• готовиться к чему? = to prepare for what?
• к осени = for autumn

The noun changes like this:

• осень → осени

So к осени means for autumn or more literally toward autumn in the sense of preparing for its arrival.

Yes, Russian could leave it out.

Because the verb ending already shows first person plural:

• покупаем
• готовимся

Both clearly mean we.

So Russian could say:

• В конце августа обычно покупаем тетради и готовимся к осени.

That would still be understandable.

But including мы is also completely natural. Russian often includes subject pronouns for:

• clarity
• emphasis
• contrast
• natural rhythm

So both versions are possible.

Yes, Russian word order is fairly flexible.

This sentence starts with the time expression:

• В конце августа

That is very natural, because it sets the scene first: when?

Then:

• мы обычно покупаем тетради и готовимся к осени

A different order is also possible, for example:

• Мы обычно в конце августа покупаем тетради и готовимся к осени.

The basic meaning stays the same, but the emphasis shifts a little.

The original order sounds very natural and neutral: first time, then who, then what usually happens.

Both are imperfective forms.

That is what Russian normally uses for:

• repeated actions
• habits
• general routines
• ongoing processes

Since the sentence includes обычно (usually), the imperfective is exactly what you would expect.

A perfective verb would suggest a single completed event or a finished result, which does not fit as well with a habitual statement.

So the sentence is about a regular pattern, not one finished occasion.

Because Russian has no articles.

So Russian does not have direct equivalents of English a, an, and the as normal articles.

That means:

• тетради can mean notebooks, the notebooks, or sometimes some notebooks
• the exact nuance comes from context

In this sentence, the general idea is simply that we usually buy notebooks.

In Russian, the names of months are normally written with a lowercase letter:

• август
• сентябрь
• октябрь

This is different from English, where August is capitalized.

So августа with a lowercase letter is correct Russian spelling.

It means the season English calls either autumn or fall.

Russian has just the standard word:

• осень

So if the English translation uses autumn or fall, both are referring to the same Russian word. There is no separate everyday Russian word that matches the British/American distinction.