من پرده را باز کردم تا بالکن را ببینم و خواهرم گفت که آینه روی دیوار خوب است.

را marks a specific direct object in Persian.

So in this sentence:

• پرده را = the curtain
• بالکن را = the balcony

It shows that these are definite/specific things, not just any curtain or any balcony.

A rough comparison:

• پرده باز کردم could sound less specific or unnatural in this context
• پرده را باز کردم = I opened the curtain
• بالکن را ببینم = so that I could see the balcony

English does not have a direct equivalent of را, so this is something learners usually just have to get used to.

باز کردم is a very common Persian verb pattern: a non-verbal element + کردن.

Here:

• باز = open
• کردم = I did

So literally it is something like I did open, but naturally it means I opened.

This is called a compound verb. Persian uses many of these:

• تمیز کردم = I cleaned
• خاموش کردم = I turned off
• باز کردم = I opened

So پرده را باز کردم is the normal way to say I opened the curtain.

In this sentence, تا means so that, in order to, or so I could.

So:

• پرده را باز کردم تا بالکن را ببینم
• I opened the curtain so that I could see the balcony

This use of تا introduces a purpose clause.

It does not mean until here. Persian تا can mean different things depending on context:

• تا فردا = until tomorrow
• تا ببینم = so that I may see / in order to see

After تا in a purpose clause, Persian usually uses the subjunctive form.

Here:

• ببینم = that I see / so that I may see

This is why Persian does not use a plain present form like می‌بینم here.

Compare:

• می‌بینم = I see / I am seeing
• ببینم = I may see / I can see / so that I see

So:

• تا بالکن را ببینم = so that I could see the balcony

This is a very common pattern:

• آمدم تا کمک کنم = I came to help
• رفتم تا او را ببینم = I went to see him/her

Yes, in many cases من is optional, because the verb already shows the subject:

• کردم already means I did
• ببینم also matches I

So the sentence could often work without من:

• پرده را باز کردم تا بالکن را ببینم...

When من is included, it may add a little emphasis, contrast, or clarity. For example:

• من opened the curtain...
• As for me, I opened the curtain...

Persian often drops subject pronouns unless they are needed for emphasis or clarity.

خواهرم means my sister.

It is made from:

• خواهر = sister
• ـم = my

So Persian often attaches possessive endings directly to nouns:

• خواهرم = my sister
• برادرم = my brother
• کتابم = my book

This is much more compact than English. You do not need a separate word for my here.

که here means that and introduces a reported clause.

So:

• خواهرم گفت که...
• My sister said that...

The word که is very common in Persian for connecting clauses.

In everyday Persian, it can sometimes be omitted, especially in speech, but using it is very normal and clear.

For example:

• گفت که می‌آید = He/She said that he/she is coming
• فکر می‌کنم که درست است = I think that it is correct

So in your sentence, که introduces what the sister said.

Persian word order is generally subject/object/other elements + verb at the end.

So:

• آینه = the mirror
• روی دیوار = on the wall
• خوب است = is good

Literally, this is something like:

• The mirror on the wall good is

That is normal Persian order. The main thing to remember is that the verb, including است, often comes at the end.

روی دیوار means on the wall.

Breakdown:

• روی = on / on top of / on the surface of
• دیوار = wall

So آینه روی دیوار means the mirror on the wall or the mirror that is on the wall.

In context, it is describing the location of the mirror.

Persian does not have a word exactly like English the.

So nouns often appear without an article, and definiteness is understood from context.

For example:

• آینه can mean a mirror or the mirror
• دیوار can mean a wall or the wall

In this sentence, the meaning is naturally understood as something specific, especially from context:

• آینه روی دیوار خوب است = The mirror on the wall is good

So Persian relies much more on context than English does for a/the distinctions.

The sentence begins with past actions:

• باز کردم = I opened
• گفت = my sister said

But inside what the sister said, the statement is:

• آینه روی دیوار خوب است = the mirror on the wall is good

This is present tense because it expresses the content of her statement as a current fact or opinion.

This is similar to English:

• My sister said that the mirror on the wall is good.

English sometimes shifts tense in reported speech, but Persian often keeps the tense that matches the meaning directly.

Yes. Very normal.

• خوب = good
• است = is

So:

• خوب است = is good

This is one of the most common adjective + است patterns in Persian:

• بزرگ است = it is big
• سخت است = it is difficult
• خوب است = it is good

In informal spoken Persian, است is often shortened or dropped in pronunciation:

• خوبه instead of خوب است

But in standard written Persian, خوب است is perfectly normal.

Not in this sentence.

Although تا can sometimes mean until, here the structure clearly shows purpose, not a time limit.

Because the sentence says:

• I opened the curtain so that I could see the balcony

That is an intentional action with a goal. The subjunctive ببینم strongly supports this purpose meaning.

If Persian wanted to emphasize until, the context and structure would normally be different.

So here, the correct interpretation is in order to see, not until I see.