Через час приехала девушка и осторожно посмотрела на крыло.

Here через час means an hour later or in an hour from some reference point in the story.

This is a very common Russian pattern:

• через минуту = in a minute
• через день = a day later
• через неделю = in a week

So через + accusative is often used to show that something happens after a certain amount of time has passed.

It does not mean physical movement through an hour here, even though через can also mean through/across in other contexts.

Because the subject is девушка, which is grammatically feminine.

In the past tense, Russian verbs agree with the subject in gender and number:

• приехал = he arrived
• приехала = she arrived
• приехало = it arrived
• приехали = they arrived

So:

• девушка приехала
• мужчина приехал

This is one of the most noticeable features of the Russian past tense.

Both can mean arrived, but they suggest different ways of getting there.

• приехать usually means to arrive by transport or by some kind of ride: car, train, bus, etc.
• прийти means to arrive on foot

So приехала девушка suggests that the girl/woman came by some means of transport, or at least the verb presents her arrival that way.

Russian word order is flexible. Both are possible, but they sound slightly different.

• Девушка приехала is more neutral if you are simply talking about the girl.
• Приехала девушка often presents the arrival itself first, and then introduces the girl as the one who arrived.

This kind of order is very common in narration. It can make the sentence sound more story-like or natural in context.

Осторожно is an adverb meaning carefully, cautiously, or with caution.

It describes how she looked:

• посмотрела = looked
• осторожно посмотрела = looked carefully / cautiously

It comes from the adjective осторожный = careful, cautious.

Compare:

• осторожный человек = a cautious person
• осторожно говорить = to speak carefully
• осторожно смотреть = to look cautiously

Because the verb смотреть / посмотреть normally uses на + accusative when it means to look at something.

So:

• смотреть на кого? на что?
• посмотреть на кого? на что?

Examples:

• смотреть на дом = to look at the house
• посмотреть на птицу = to look at the bird

That is just the standard pattern of the verb.

It is in the accusative singular, because на after посмотреть takes the accusative.

However, for an inanimate neuter noun like крыло, the accusative form is the same as the nominative:

• nominative: крыло
• accusative: крыло

So the form does not change, but the case is still accusative because of the grammar of посмотреть на.

Because Russian, like English, does not need to repeat the subject if it is the same person.

So:

• приехала девушка и осторожно посмотрела на крыло

means:

• A girl arrived and [she] carefully looked at the wing

The subject девушка applies to both verbs:

• приехала
• посмотрела

Repeating девушка would usually be unnecessary.

Both verbs present the actions as completed single events.

• приехала = she arrived
• посмотрела = she took a look / looked

This fits a narrative sequence well: one finished action happened, then another finished action happened.

Their imperfective partners would be:

• приезжала = was arriving / used to arrive / came on some occasion
• смотрела = was looking / looked for some time

In this sentence, the perfective aspect makes the story move forward step by step.

Usually not. Perfective посмотрела often suggests a single completed look or brief act of looking.

If you want to emphasize that she was looking for some time, Russian would more naturally use the imperfective:

• смотрела на крыло

So осторожно посмотрела is something like carefully took a look at.

Крыло most commonly means wing, but the exact meaning depends on context.

It can refer to:

• a bird’s wing
• an airplane wing
• a building wing

Without more context, Russian does not tell you which one it is. The sentence itself only says that she looked at the wing.

Not always. Девушка can mean:

• girl
• young woman
• sometimes even a polite way to address a woman in everyday speech

So the best English choice depends on context, age, and tone. In many narrative sentences, young woman may sound more natural than girl, depending on the situation.

Russian has no articles. Nouns appear without words corresponding directly to a/an and the.

So девушка can mean:

• a girl
• the girl

and крыло can mean:

• a wing
• the wing

Which one is intended is understood from context, word order, and the surrounding story. This is normal in Russian and is something English speakers have to get used to.