Я работаю, в то время как друг покупает дневной пропуск.

Yes, Russian often drops subject pronouns because the verb ending already shows who is doing the action. So Работаю by itself can mean I am working.

However, Я работаю is still completely natural. Speakers may include Я for clarity, contrast, or emphasis. In this sentence, Я работаю sounds perfectly normal.

Работаю is the 1st person singular present tense form of работать (to work).

So:

• я работаю = I work / I am working

In Russian, the present tense can often translate as either simple present or present continuous in English, depending on context.

It can mean either one. Russian does not have a separate am working form the way English does.

So Я работаю may mean:

• I work
• I am working

The context decides which English translation sounds best.

В то время как is a conjunction meaning something like:

• while
• whereas
• at the same time that

In this sentence, it connects two actions happening at the same time.

It is grammatical and clear, but it can sound a bit more formal or bookish than just пока in everyday speech.

For example:

• Я работаю, в то время как друг покупает пропуск.
• Я работаю, пока друг покупает пропуск.

Both can work, though пока is often more conversational.

Yes, in many situations you could.

• Я работаю, пока друг покупает дневной пропуск.

This usually sounds more natural in everyday spoken Russian.

But there is a small nuance:

• пока often strongly suggests while / during the time that
• в то время как can sound more explicitly like while, and sometimes even whereas in more formal writing

So your original sentence is correct, but пока may sound more natural in conversation.

Russian often leaves out possessive words like my when they are understood from context.

So:

• друг = friend
• мой друг = my friend

In English, my friend is often required, but in Russian just друг can be enough if it is obvious whose friend is meant.

Still, мой друг would also be correct:

• Я работаю, в то время как мой друг покупает дневной пропуск.

That version is a bit more explicit.

Because друг is the subject of the second clause:

• друг покупает = the friend is buying / buys

Subjects are normally in the nominative case in Russian.

So here:

• Я is the subject of работаю
• друг is the subject of покупает

Покупает is the 3rd person singular present tense form of покупать (to buy).

So:

• друг покупает = the friend buys / is buying

Again, Russian present tense can correspond to either English buys or is buying, depending on context.

Because покупать is the imperfective verb, and купить is the perfective partner.

Here is the difference:

• покупать = buying, process, repeated action, or general action
• купить = to buy successfully / complete the purchase

In the present tense, perfective verbs usually refer to the future, so:

• друг покупает = the friend is buying / buys
• друг купит = the friend will buy

So if the meaning is about what is happening now, покупает is the right choice.

Дневной means daytime, daily, or for one day, depending on context.
Пропуск can mean pass, permit, or entry pass.

So дневной пропуск means a day pass or one-day pass.

The exact English translation depends on the situation:

• a pass for one day
• a daytime pass
• an entry pass valid for the day

Because it is the direct object of покупает:

• покупает что? = what is he buying?
• дневной пропуск

In Russian, inanimate masculine nouns often have the same form in the nominative and accusative singular.

So:

• nominative: дневной пропуск
• accusative: дневной пропуск

That is why the form does not change here.

Yes. Russian word order is more flexible than English word order.

Your sentence is normal:

• Я работаю, в то время как друг покупает дневной пропуск.

But other orders are also possible, depending on emphasis, for example:

• В то время как друг покупает дневной пропуск, я работаю.
• Друг покупает дневной пропуск, в то время как я работаю.

The meaning stays similar, but the focus can shift slightly.

It is grammatical and understandable, but it sounds a little formal because of в то время как and possibly because дневной пропуск is somewhat context-specific.

A more everyday version might be:

• Я работаю, пока мой друг покупает пропуск.

Or, depending on the situation:

• Я работаю, пока друг покупает билет на день.

So the original sentence is correct, but not necessarily the most casual way a native speaker would always say it.

In careful speech, it is pronounced word by word, but in normal connected speech it flows together more smoothly. A learner should pay attention to stress:

• в то врЕмя как

The main stress is on врЕмя.

Also, the в before то is unstressed and short. Native speech may make the whole phrase sound fairly compact.

Yes. A comma is normally used before как in the conjunction в то время как, because it introduces a subordinate clause.

So this punctuation is correct:

• Я работаю, в то время как друг покупает дневной пропуск.

If the subordinate clause comes first, you still use a comma:

• В то время как друг покупает дневной пропуск, я работаю.