אל תיכנסו לחדר עד שהמנהל יסיים את השיחה.

Because אל is used for a negative command in Hebrew.

• אל תיכנסו = Don’t enter
• לא תיכנסו would usually mean you will not enter or you do not enter, not a direct command.

So if you want to tell someone don’t do something, Hebrew commonly uses:

• אל
  • future-form verb

That is exactly what happens here with אל תיכנסו.

In Hebrew, negative commands are often formed with:

• אל
  • a verb in the future tense

So even though תיכנסו is formally a future-tense form, in this sentence it functions as an instruction:

• תיכנסו = you will enter / you enter
• אל תיכנסו = don’t enter

This is a very common pattern in Hebrew grammar.

תיכנסו is second person masculine plural.

That means the speaker is talking to:

• a group of men, or
• a mixed group of people

In everyday modern Hebrew, masculine plural is often also used for mixed groups.

Related forms:

• תיכנס = you will enter / enter! (to one male)
• תיכנסי = to one female
• תיכנסו = to more than one person

So this sentence is directed at more than one person.

תיכנסו comes from the root כ-נ-ס and the verb להיכנס, which means to enter.

This verb is in the pattern called נפעל.

A few useful forms:

• להיכנס = to enter
• נכנס = entered / enters
• ייכנס = he will enter
• תיכנסו = you (plural) will enter

The ל־ in לחדר shows where someone enters:

• להיכנס לחדר = to enter the room

So the structure is very natural: אל תיכנסו לחדר = Don’t enter the room.

After the verb להיכנס (to enter), Hebrew usually uses the preposition ל־ (to / into) before the place entered.

So:

• להיכנס לחדר = to enter the room
• literally something like to enter to/into the room

In English, we just say enter the room, without a preposition, but Hebrew normally needs one here.

Also notice that ל + ה often combines into one form:

• ל + החדר becomes לחדר

So לחדר means to the room / into the room.

עד means until.

When it is followed by a full clause, Hebrew often uses ש־ after it:

• עד ש... = until...

So:

• עד שהמנהל יסיים את השיחה = until the manager finishes the conversation

The ש־ here works like that / when introducing the clause after until.

This structure is very common in Hebrew:

• חכה עד שאני אבוא = Wait until I come
• אל תלך עד שהם יגיעו = Don’t go until they arrive

Hebrew often uses the future tense after words like עד ש־ when talking about something that has not happened yet.

So:

• עד שהמנהל יסיים = until the manager finishes / will finish

Even though English may sometimes use the present tense after until (until the manager finishes), Hebrew naturally uses a future form here because the action is still ahead in time.

That is why יסיים is correct.

יסיים means he will finish.

It comes from the verb לסיים = to finish.

A few related forms:

• לסיים = to finish
• סיים = he finished
• מסיים = finishing / finishes
• יסיים = he will finish

Here, the subject is המנהל (the manager), so יסיים means:

• the manager will finish

In Hebrew, את marks a definite direct object.

Since השיחה means the conversation and is definite because of ה־ (the), Hebrew uses את before it:

• יסיים את השיחה = finish the conversation

Compare:

• הוא קורא ספר = He is reading a book
• הוא קורא את הספר = He is reading the book

So in your sentence:

• את השיחה is correct because it means the conversation, a specific known conversation.

The prefix ה־ is the Hebrew word the.

So:

• מנהל = manager
• המנהל = the manager

and

• שיחה = conversation
• השיחה = the conversation

In this sentence, both nouns are definite:

• the manager
• the conversation

That is why both take ה־.

שיחה can mean several related things depending on context:

• conversation
• talk
• discussion
• sometimes phone call

In this sentence, without more context, the conversation is the safest general translation.

If the situation is clearly about someone speaking on the phone, it could also mean:

• until the manager finishes the phone call

So the Hebrew word is a little broader than just one English option.

Yes. אל תיכנסו לחדר... is perfectly normal, but it can sound like a direct instruction.

A softer version might be:

• בבקשה אל תיכנסו לחדר עד שהמנהל יסיים את השיחה = Please don’t enter the room until the manager finishes the conversation

Or:

• חכו בבקשה עד שהמנהל יסיים את השיחה = Please wait until the manager finishes the conversation

So the original sentence is natural, but adding בבקשה or rephrasing with wait can sound more polite.

You would change the verb form to match the person’s gender and number.

To one male:

• אל תיכנס לחדר עד שהמנהל יסיים את השיחה

To one female:

• אל תיכנסי לחדר עד שהמנהל יסיים את השיחה

To several people:

• אל תיכנסו לחדר עד שהמנהל יסיים את השיחה

So the main change is in the command verb תיכנסו / תיכנס / תיכנסי. The rest of the sentence stays the same.