Сестра оформила возврат, потому что обмен на другой размер оказался невозможен.

My sister arranged a return because an exchange for another size turned out to be impossible.

Breakdown of Сестра оформила возврат, потому что обмен на другой размер оказался невозможен.

• сестра: the sister
• на: for
• потому что: because
• другой: another

Questions & Answers about Сестра оформила возврат, потому что обмен на другой размер оказался невозможен.

Why is оформила feminine?

Because the subject is сестра, which is a feminine noun.

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

• оформил = he processed / arranged
• оформила = she processed / arranged
• оформило = it processed / arranged
• оформили = they processed / arranged

So Сестра оформила возврат means The sister processed/arranged the return.

What does оформить возврат mean exactly?

Оформить often means to process, arrange, make official, fill out properly.
So оформить возврат is not just to return something, but more specifically to process a return or to arrange the return formally.

This is common in store/customer-service language.

Compare:

• вернуть товар = to return the item
• оформить возврат = to process the return / complete the return procedure

So this sentence sounds like a retail or service situation.

Why use возврат instead of a verb like вернула?