Я заранее поменял валюту, потому что в аэропорту курс обычно хуже.

Поменял is perfective, so it presents the exchange as a completed action: I exchanged it.

If you said менял, that would be imperfective and would usually suggest a process, repetition, or no emphasis on completion. In this sentence, the speaker means they took care of it beforehand, so the completed action is the important idea.

• Я заранее поменял валюту = I exchanged the currency in advance.
• Я заранее менял валюту would sound unusual here unless there were some special context.

In everyday Russian, поменять валюту often means to exchange money / currency.

Literally, поменять can mean to change or to swap, but with валюта or деньги in the right context, it commonly means to exchange money, for example at a bank or exchange office.

So here:

• поменял валюту = exchanged currency
• not just changed in a vague sense

A more explicit version could be:

• обменял валюту
• обменял деньги

But поменял валюту is very natural in speech.

Because it is the direct object of the verb поменял.

The dictionary form is валюта. Since it is a feminine noun and it is the thing being exchanged, it goes into the accusative singular:

• nominative: валюта
• accusative: валюту

So:

• Я поменял валюту = I exchanged currency

Заранее means in advance / ahead of time / beforehand.

It is an adverb, so it describes the action поменял. In this sentence, it tells us when the speaker exchanged the currency.

Russian word order is flexible, so you can move it around:

• Я заранее поменял валюту
• Я поменял валюту заранее
• Заранее я поменял валюту

All are possible, but they may shift emphasis slightly. The version in your sentence is very natural and neutral.

Because потому что introduces a subordinate clause: because...

Russian normally uses a comma before subordinate clauses, including clauses with потому что.

So:

• Я заранее поменял валюту, потому что...

This is standard punctuation.

Yes, in sentences like this, потому что is the standard way to say because.

It introduces the reason:

• Я заранее поменял валюту, потому что в аэропорту курс обычно хуже.
• I exchanged currency in advance because the rate is usually worse at the airport.

Russian also has other ways to express cause, but потому что is the most straightforward and common one for learners.

Because the sentence is talking about location, not movement.

• в аэропорту = in/at the airport
• в аэропорт = to the airport

Here, the meaning is at the airport, the rate is usually worse, so a location form is needed.

Also, аэропорт has the special locative form в аэропорту, which is very common after в when talking about location.

This is a good question because Russian has a special form here.

For some masculine nouns, especially place words, Russian uses a special locative ending -у / -ю after в or на when talking about location.

So:

• в аэропорту = at the airport

This is the standard form in modern Russian.

You may learn that the prepositional of аэропорт is об аэропорте (about the airport), but after в for location, Russian usually prefers в аэропорту.

Compare:

• говорить об аэропорте = to talk about the airport
• быть в аэропорту = to be at the airport

Because курс by itself often already means exchange rate in this kind of context.

Since the sentence is about money and exchanging currency, Russian speakers easily understand:

• курс = the exchange rate

If you want to be more explicit, you can say:

• обменный курс

But in everyday speech, курс is often enough.

Хуже means worse. It is the comparative form of плохой (bad) or sometimes corresponds to badly depending on the structure.

In this sentence:

• курс обычно хуже = the rate is usually worse

So хуже is comparing the airport rate with the rate somewhere else, even though that second point of comparison is not stated directly.

Russian does not always need to state the second half of a comparison if it is obvious from context.

Here, the meaning is something like:

• в аэропорту курс обычно хуже, чем в городе / в банке / заранее
• at the airport the rate is usually worse than in town / at a bank / if you do it earlier

Because the listener can easily infer the comparison, хуже can stand on its own.

English does this too sometimes:

• The rate is usually worse at the airport.

Обычно means usually, and it modifies the whole statement курс хуже.

So:

• курс обычно хуже = the rate is usually worse

This placement is very natural. Russian adverbs like обычно often come before the word or phrase they modify, but word order is flexible.

For example:

• В аэропорту курс обычно хуже
• В аэропорту обычно курс хуже

The first version sounds more natural here.

Yes, я could be omitted if the context already makes the subject clear.

Russian often drops subject pronouns when they are obvious:

• Заранее поменял валюту, потому что в аэропорту курс обычно хуже.

However, including я is perfectly normal and often sounds clearer, especially as a standalone sentence.

So:

• Я included = explicit, clear, neutral
• Я omitted = possible if the context already tells us who is speaking

That is the past tense marker in Russian.

Russian past tense verbs are formed from the infinitive stem plus -л, and they also agree in gender and number.

From поменять:

• masculine: поменял
• feminine: поменяла
• neuter: поменяло
• plural: поменяли

So Я заранее поменял валюту suggests the speaker is male. A female speaker would say:

• Я заранее поменяла валюту

Yes, absolutely.

Both can work, but there is a slight nuance:

• обменял валюту = more explicitly exchanged currency
• поменял валюту = very common in everyday speech, a bit more conversational

So both are natural:

• Я заранее поменял валюту
• Я заранее обменял валюту

A learner will often hear поменять деньги, поменять валюту, and обменять валюту.

Not exactly.

Валюта means currency, often especially foreign currency or a particular type of currency.
Деньги means money in a broader sense.

So:

• поменять деньги = exchange money
• поменять валюту = exchange currency

In this sentence, валюту is used because the situation is specifically about exchange rates and changing one currency into another.

Yes. Russian word order is flexible, and changing it usually changes emphasis rather than basic meaning.

For example:

• Я заранее поменял валюту, потому что в аэропорту курс обычно хуже.
  Neutral, very natural.

• Валюту я поменял заранее, потому что в аэропорту курс обычно хуже.
  More emphasis on валюту.

• Потому что в аэропорту курс обычно хуже, я заранее поменял валюту.
  More emphasis on the reason.

The original version is a very good neutral model for learners.

A female speaker would say:

• Я заранее поменяла валюту, потому что в аэропорту курс обычно хуже.

The only change is:

• поменял → поменяла

That is because Russian past tense verbs agree with the speaker’s gender in the singular.