در اتاق خواب یک آینه بزرگ روی دیوار هست.

Because Persian often puts the setting first, especially the place.
So در اتاق خواب means in the bedroom, and it sets the scene before telling you what exists there.

A natural way to feel the structure is:

In the bedroom, there is a big mirror on the wall.

Persian word order is flexible, but this location-first order is very common and natural.

اتاق خواب means bedroom.

Literally, it is:

• اتاق = room
• خواب = sleep

So the literal sense is something like sleeping room.

It is pronounced otâq-e xâb. That little -e sound between the two words is very important.

That -e is called ezafe. Persian usually does not write ezafe in normal spelling, but speakers still pronounce it.

So although you see:

اتاق خواب

you usually pronounce it:

otâq-e xâb

The same thing happens elsewhere in this sentence too:

• آینه بزرگ → âyene-ye bozorg
• روی دیوار → ru-ye divâr

So one important learner skill is noticing hidden ezafe.

It can mean both, depending on context.

Here, یک is functioning like a/an:

• یک آینه بزرگ = a big mirror

Literally, یک means one, but in many sentences it also works as the indefinite article.

So in this sentence, it is best understood as a rather than emphasizing the number one.

Sometimes yes, but یک is very common and very natural in this kind of sentence.

With a singular countable noun in an existential sentence like there is a..., Persian often uses یک:

• یک آینه بزرگ ... هست = there is a big mirror ...

If you omit it, the sentence may sound less natural or more context-dependent. For a learner, using یک here is the safest choice.

Because in Persian, adjectives usually come after the noun.

So:

• آینه بزرگ = mirror big = big mirror

More precisely, there is a hidden ezafe link:

• آینه‌ی بزرگ
• pronounced âyene-ye bozorg

This is the normal Persian pattern:

• خانه بزرگ = big house
• کتاب خوب = good book
• آینه بزرگ = big mirror

Because روی دیوار is a prepositional phrase that tells you where the mirror is.

So the noun phrase comes first:

• یک آینه بزرگ = a big mirror

Then its location:

• روی دیوار = on the wall

Together:

• یک آینه بزرگ روی دیوار = a big mirror on the wall

This is similar to English in meaning, even if the overall sentence order is a bit different.

It means on the wall.

Parts:

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

In pronunciation, there is again a hidden ezafe:

• روی دیوار → ru-ye divâr

So you will often hear:

ru-ye divâr

Even though the spelling usually does not show that connecting sound.

هست means is or exists, and in this sentence it gives an existential meaning:

there is

So the structure is basically:

• در اتاق خواب ... هست
• In the bedroom ... there is

In English, we need the dummy word there in there is. Persian does not need that. It can simply use the noun phrase plus هست.

So:

• یک آینه بزرگ روی دیوار هست
• literally: a big mirror on the wall is
• natural English: there is a big mirror on the wall

They are related, but they are not always used in exactly the same way.

In many situations:

• است = is
• هست = is / exists

In a sentence like this one, which is about the existence of something in a place, هست is very natural:

• در اتاق خواب یک آینه بزرگ روی دیوار هست

Using هست helps give the sense of there is.

No, not in this sentence.

English says:

• There is a big mirror on the wall

But Persian does not need a separate word like that there. Instead, it uses the structure:

• place + thing + هست

So Persian expresses the same idea without a dummy subject.

A natural pronunciation is:

dar otâq-e xâb yek âyene-ye bozorg ru-ye divâr hast

You can hear the hidden connectors if you break it up:

• dar
• otâq-e xâb
• yek âyene-ye bozorg
• ru-ye divâr
• hast

Yes, Persian word order is somewhat flexible, but not every version sounds equally natural.

This sentence is very natural because it goes:

1. place
2. thing
3. more specific location
4. verb

So:

در اتاق خواب یک آینه بزرگ روی دیوار هست

Another possible order is:

در اتاق خواب، روی دیوار یک آینه بزرگ هست

This is also natural and puts a bit more focus on on the wall.

So the order can change, but the original sentence is a very normal way to say it.

No. Persian nouns do not have grammatical gender.

So آینه is not masculine or feminine, and neither are اتاق or دیوار.

That is one thing English speakers often find pleasantly simple about Persian.