Перед отправкой я перечитал курсовую ещё раз и исправил одну ошибку.

It means before submitting / before sending it off.

Literally, перед means before or in front of, and отправкой comes from отправка (sending, submission, dispatch). In this sentence, it refers to the time before the submission.

So:

• перед отправкой = before submission
• more naturally in English here: before submitting it

Because the preposition перед normally takes the instrumental case.

So:

• nominative: отправка
• instrumental: отправкой

This is a very common pattern:

• перед уроком = before the lesson
• перед экзаменом = before the exam
• перед отправкой = before submission

Перечитал means reread.

It comes from перечитать:

• читать = to read
• прочитать = to read through, to read completely
• перечитать = to read again, reread

So the prefix пере- here adds the idea of again.

In this sentence, the speaker is saying they looked through the paper one more time before sending it, so перечитал is exactly the right choice.

Because it is the direct object of перечитал, so it is in the accusative case.

The full phrase is usually:

• курсовая работа = term paper / course paper

But in everyday Russian, people often shorten this to just:

• курсовая

When declined in the accusative singular feminine, it becomes:

• курсовую

So:

• я перечитал курсовую = I reread my term paper

Yes, it is completely normal.

Курсовая is a very common shortened form of курсовая работа. Russian often drops the noun when the adjective has become a familiar standalone word.

Similar idea in English:

• final for final exam
• midterm for midterm exam

So курсовую here naturally means the term paper.

Ещё раз means once more, again, or one more time.

In this sentence:

• перечитал ... ещё раз = reread ... one more time

Even though перечитал already contains the idea of reading again, ещё раз adds emphasis and makes it sound more natural:

• перечитал = reread
• перечитал ещё раз = reread one more time

A little, but in a natural way.

Russian often uses both a prefixed verb and an extra adverbial phrase like ещё раз for emphasis or smoothness.

So this sounds very normal:

• я перечитал курсовую ещё раз

It suggests something like:

• I gave my term paper one more read-through

It is not awkward in Russian.

Because исправил is perfective, and it presents the action as completed.

Compare:

• исправлял = was correcting / used to correct / corrected (process-focused)
• исправил = corrected, fixed (result-focused)

Here the speaker means that they actually found and fixed one error before submitting the paper. The result matters, so исправил is the natural choice.

Because ошибка is a feminine noun, and here it is in the accusative singular as the direct object of исправил.

Forms:

• nominative: одна ошибка = one mistake
• accusative: одну ошибку = one mistake

So:

• исправил одну ошибку = corrected one mistake

Not necessarily.

It usually means the speaker corrected one particular mistake at that moment. It does not always mean that there was only one mistake total.

Depending on context, it could mean:

• they found just one error during this final rereading
• they are simply mentioning one corrected error, not giving a full count of all errors

Because перечитал and исправил are two verbs with the same subject (я) joined by и.

This is a standard case of a compound predicate:

• я перечитал ... и исправил ...

No comma is needed.

It is in the past tense.

The past-tense verbs are:

• перечитал
• исправил

In Russian, past tense is formed from the infinitive stem plus endings that reflect gender/number.

Here both forms are masculine singular, which means the speaker is presented as male.

If the speaker were female, it would be:

• я перечитала курсовую ещё раз и исправила одну ошибку

From the past-tense verb endings:

• перечитал
• исправил

These are masculine singular past forms.

Russian past tense agrees with the subject in gender and number when the subject is singular.

So:

• male speaker: перечитал, исправил
• female speaker: перечитала, исправила

Yes. Russian word order is flexible, though each version has a slightly different emphasis.

The original sentence is very natural:

• Перед отправкой я перечитал курсовую ещё раз и исправил одну ошибку.

Other possible versions:

• Я перед отправкой перечитал курсовую ещё раз и исправил одну ошибку.
• Курсовую я перед отправкой перечитал ещё раз и исправил одну ошибку.

The meaning stays basically the same, but the focus shifts a bit depending on what comes first.

Yes, Russian often omits subject pronouns when they are clear from the verb form.

So you could say:

• Перед отправкой перечитал курсовую ещё раз и исправил одну ошибку.

That would still be understandable, especially in context.

However, including я is also completely natural. It can make the sentence a little clearer or more explicit.

It can mean both, depending on context.

In this sentence, because we are talking about a курсовая, отправка naturally means something like:

• submission
• sending it in
• turning it in electronically

So Перед отправкой is best understood as before submitting it rather than physical shipping.

Because the sentence presents a sequence of completed actions before submission:

1. he reread the paper
2. he corrected one mistake

Perfective verbs are commonly used when narrating completed steps in order.

So the sentence has a clear result-based feel:

• I reread the paper once more and fixed one mistake before submitting it.

That is why perfective aspect works so well here.