אם את רוצה להתרכז, תסגרי את הדלת ואל תפריעי לאחותך.

Because it is being said to one female.

You can see that in:

• את = you (feminine singular)
• רוצה = want (feminine singular form)
• תסגרי = you will close / close! (to one female)
• תפריעי = you will disturb / disturb! (to one female)

If you were speaking to a male, it would be:

אם אתה רוצה להתרכז, תסגור את הדלת ואל תפריע לאחותך.

So Hebrew marks gender much more often than English does.

אם means if.

It introduces the condition:

• אם את רוצה להתרכז = if you want to concentrate

Then the rest of the sentence gives the result or instruction:

• תסגרי את הדלת ואל תפריעי לאחותך = close the door and don’t disturb your sister

So the whole structure is:

אם ... , ...
If ..., then ...

In Hebrew, אם את רוצה literally means if you want or if you do want. It describes a current state or desire.

So:

• אם את רוצה להתרכז = if you want to concentrate

This is very natural in Hebrew.

You could also hear אם תרצי להתרכז, which is more like:

• if you’ll want to concentrate
• if you decide you want to concentrate

But in this sentence, אם את רוצה sounds very normal and straightforward.

להתרכז is the infinitive, meaning to concentrate.

The prefix ל־ often corresponds to English to before a verb:

• להתרכז = to concentrate
• ללכת = to go
• לסגור = to close

So:

• רוצה להתרכז = want to concentrate

Also, להתרכז is from the reflexive-style pattern often used for actions a person does to or with themselves, so it has the sense of focus oneself / concentrate.

Here, את is the pronoun you.

That can be confusing, because Hebrew also has את as the direct object marker.

In this sentence, there are actually two different words spelled את:

1. אם את רוצה
   Here את = you (feminine singular), pronounced at

2. תסגרי את הדלת
   Here את is the direct object marker, pronounced et

So the meaning depends on the role in the sentence.

Here את is the direct object marker. It has no separate English translation, but it marks a definite direct object.

So:

• הדלת = the door
• את הדלת = marks the door as the definite thing being closed

That is why Hebrew says:

• תסגרי את הדלת = close the door

But if the object were indefinite, Hebrew usually would not use את:

• תסגרי דלת = close a door or close some door
  though in real life this exact phrasing is less common

So את appears because הדלת is definite: the door.

Good question. In Modern Hebrew, people very often use the future form as a command, especially in everyday speech.

So both are possible:

• סגרי את הדלת = formal/standard imperative
• תסגרי את הדלת = very common spoken command

The future-form command can sound more natural in everyday conversation and sometimes a bit less abrupt.

So here:

• תסגרי is literally a future form
• but functionally it means close!

Because Hebrew normally makes a negative command with:

אל + future form

So:

• אל תפריעי = don’t disturb
• אל תסגרי = don’t close

By contrast, לא תפריעי usually means:

• you will not disturb or
• you won’t disturb

That is a statement about the future, not the normal way to give a negative command.

So:

• אל תפריעי = command
• לא תפריעי = future negation

The ו־ means and.

So:

• ואל תפריעי = and don’t disturb

This is just:

• ו = and
• אל = the negative-command word don’t

Together they make:

• ו + אל = and don’t

לאחותך means to your sister.

It is built from three parts:

• ל־ = to
• אחות = sister
• ־ךְ = your (feminine singular, because the sentence is addressed to a female)

So:

• לאחותך = to your sister

In this sentence, English says disturb your sister, but Hebrew uses the verb with ל־:

• להפריע ל... = to disturb / bother ...

So literally:

• אל תפריעי לאחותך = don’t interfere with / bother your sister

The prefix ה־ means the.

So:

• דלת = door
• הדלת = the door

Since the sentence means close the door, Hebrew uses the definite form הדלת.

And because it is definite, it also takes the direct object marker:

• את הדלת

Because Hebrew verb forms usually already show the person, number, and often gender.

So:

• תסגרי already means you (one female) close / will close
• תפריעי already means you (one female) disturb / will disturb

That is why Hebrew often omits the pronoun unless it is needed for emphasis or contrast.

So Hebrew does not need to say:

• את תסגרי
• את תפריעי

unless the speaker wants extra emphasis.

Here are the main versions:

To one male:
אם אתה רוצה להתרכז, תסגור את הדלת ואל תפריע לאחותך.

To one female:
אם את רוצה להתרכז, תסגרי את הדלת ואל תפריעי לאחותך.

To a group of males or a mixed group:
אם אתם רוצים להתרכז, תסגרו את הדלת ואל תפריעו לאחותכם.

To a group of females:
אם אתן רוצות להתרכז, תסגרו את הדלת ואל תפריעו לאחותכן.

So Hebrew changes not only the pronoun, but also the verb forms and sometimes the possessive ending in your sister.