خواهرم گفت که لباس هایش را در کمد میگذارد و نامه ها را در کشو نگه میدارد.

The -م is a possessive ending meaning my.

• خواهر = sister
• خواهرم = my sister

In Persian, possession is often shown by attaching a short ending to the noun:

• برادرم = my brother
• مادرم = my mother
• دوستم = my friend

So خواهرم گفت means my sister said.

که is a very common connector, often meaning that.

So:

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

In English, that is sometimes optional:

• My sister said that...
• My sister said...

In Persian, که is extremely common after verbs like گفت (said), فکر کرد (thought), دید (saw), etc.

This part combines plural and possession.

• لباس = clothing / clothes
• ها = plural marker
• ـیش / ـاش = his/her/its

So:

• لباس‌ها = clothes
• لباس‌هایش = his/her clothes

A few useful points:

1. ها makes the noun plural.
2. The ending ـش means his/her/its.
3. In writing, you may see this written with or without the short joining mark:
   • لباس‌هایش (more standard)
   • لباس هایش (also commonly seen)

So لباس هایش را means her clothes or his clothes as the object of the verb.

Not by itself. -ش can mean:

• his
• her
• its

Persian does not mark grammatical gender the way English does. So لباس هایش could mean:

• his clothes
• her clothes

You understand which one is meant from context. Since the subject here is خواهرم (my sister), learners will usually interpret it as her clothes.

را marks a specific direct object.

In this sentence:

• لباس هایش را = her clothes
• نامه ها را = the letters

Both are definite/specific things, so را is used.

Compare:

• کتاب می‌خوانم = I read books / I am reading a book
• کتاب را می‌خوانم = I am reading the book

So in your sentence, the speaker is talking about particular clothes and particular letters, not just clothes/letters in general.

در means in.

So:

• در کمد = in the closet / wardrobe
• در کشو = in the drawer

It is a very common preposition:

• در خانه = at home / in the house
• در مدرسه = at school
• در کیف = in the bag

They refer to two different storage places:

• کمد = closet, wardrobe, cabinet
• کشو = drawer

So the sentence contrasts two locations:

• clothes go in the closet
• letters are kept in the drawer

Because the sentence is reporting what your sister said she does or usually does, not just one completed past action.

• گفت = said (past)
• می‌گذارد = puts / places / is putting
• نگه می‌دارد = keeps

So the structure is:

• خواهرم گفت که ... = My sister said that...
• then the content of what she said is in the present/imperfective form:
  • لباس هایش را در کمد می‌گذارد
  • نامه ها را در کشو نگه می‌دارد

This is normal in Persian when reporting statements.

In more standard spelling, it is usually written with a half-space:

• می‌گذارد

You may also see:

• میگذارد

The same goes for:

• نگه می‌دارد rather than نگه میدارد

The meaning is the same. The version with the half-space is considered more standard in careful writing.

می‌ is an imperfective prefix. In many contexts it gives meanings like:

• present habitual: puts, keeps
• present ongoing: is putting, is keeping
• sometimes more general repeated action

So:

• می‌گذارد = puts / places
• نگه می‌دارد = keeps / holds

Exactly how you translate it into English depends on context.

Because نگه داشتن is a compound verb.

It consists of:

• نگه = keeping/held
• داشتن = to have / to hold

Together:

• نگه داشتن = to keep

When conjugated, the main changes happen on the second part:

• نگه می‌دارد = he/she keeps
• نگه می‌دارم = I keep
• نگه می‌دارند = they keep

This is very common in Persian. Many verbs are built this way.

They are similar but not identical.

• می‌گذارد = puts, places
• نگه می‌دارد = keeps, stores, holds onto

So the sentence suggests:

• she puts the clothes in the closet
• she keeps the letters in the drawer

The first focuses on placing something somewhere.
The second focuses on keeping/storing something there.

Because the subject is understood to be the same: خواهرم / she.

Persian often omits repeated subjects when they are clear from context.

So this part:

• لباس هایش را در کمد میگذارد و نامه ها را در کشو نگه میدارد

means:

• She puts her clothes in the closet and keeps the letters in the drawer

Persian does not need to repeat او or خواهرم before the second verb.

Yes. The sentence follows the usual Persian pattern of Subject + Object + other elements + Verb.

For example:

• خواهرم = subject
• لباس هایش را = object
• در کمد = prepositional phrase
• میگذارد = verb

Then the same pattern repeats:

• نامه ها را
• در کشو
• نگه میدارد

Persian is generally a verb-final language, so it is very normal for the verb to come at the end of each clause.

Because ها is the most common and general plural marker in Persian.

• نامه = letter
• نامه‌ها = letters

This plural ending works with many nouns:

• کتاب‌ها = books
• دوست‌ها = friends
• عکس‌ها = photos

So نامه ها را simply means the letters as a specific object.

Yes, لباس can sometimes behave like a collective noun meaning clothing/clothes in a general sense. But adding ها makes the plurality more explicit:

• لباس = clothing / a garment / clothes in a broad sense
• لباس‌ها = clothes, garments

So لباس هایش clearly means his/her clothes rather than just clothing in a more abstract sense.

A few useful points:

• خواهرم is pronounced roughly like khāharam
• می‌گذارد is roughly migozārad
• نگه می‌دارد is roughly negah midārad
• کشو is roughly keshu
• کمد is roughly komod

Also, in normal speech, learners may hear slightly smoother connected pronunciation than what the spelling suggests. That is normal in Persian.