הפגישה שלנו מתחילה מוקדם, אבל השיעור שלה מתחיל מאוחר.

Because the verb agrees with the subject noun in gender and number.

• הפגישה (the meeting) is feminine singular, so the verb is מתחילה.
• השיעור (the lesson/class) is masculine singular, so the verb is מתחיל.

So:

• הפגישה שלנו מתחילה = Our meeting starts
• השיעור שלה מתחיל = Her lesson starts

This is very common in Hebrew present tense.

That is the normal Hebrew pattern for possession in sentences like this.

English says:

• our meeting
• her lesson

Hebrew usually says:

• הפגישה שלנו = literally the meeting of ours
• השיעור שלה = literally the lesson of hers

So the possessed thing comes first, and the possessive word comes after it.

The ה־ is the definite article, meaning the.

In Hebrew, phrases like our meeting and her lesson are definite, so the noun normally takes ה־:

• הפגישה שלנו = our meeting
• השיעור שלה = her lesson

This is the normal modern Hebrew way to say it.

No. שלה does not agree with the noun being owned. It refers to the owner.

• שלה = hers / her
• שלו = his
• שלהם = their (masculine/mixed)
• שלהן = their (feminine)

So השיעור שלה means her lesson, regardless of the fact that שיעור is masculine.

The noun’s gender affects the verb:

• השיעור ... מתחיל

But the possessor word reflects whose it is:

• שלה = her

Here, מוקדם and מאוחר are being used adverbially, meaning early and late.

They describe when the action happens, not the noun itself.

So:

• הפגישה שלנו מתחילה מוקדם = Our meeting starts early
• השיעור שלה מתחיל מאוחר = Her lesson starts late

If you were describing the nouns themselves with adjectives, then you would use agreement:

• פגישה מוקדמת = an early meeting
• שיעור מאוחר = a late lesson/class

So the forms in your sentence are correct because they function like adverbs.

The dictionary form is להתחיל, which means to begin or to start.

The present-tense forms are:

• מתחיל = masculine singular
• מתחילה = feminine singular
• מתחילים = masculine plural / mixed plural
• מתחילות = feminine plural

So in your sentence:

• מתחילה matches הפגישה
• מתחיל matches השיעור

These are present-tense forms in Hebrew.

In English, depending on context, they are often translated as:

• starts
• is starting
• begins
• is beginning

In this sentence, the most natural English translation is starts:

• Our meeting starts early, but her lesson starts late.

So even though the Hebrew form is present tense, English often uses the simple present for schedules and regular facts.

In this sentence, repeating the verb is the natural and clear choice:

• הפגישה שלנו מתחילה מוקדם, אבל השיעור שלה מתחיל מאוחר.

If you removed the second מתחיל, the meaning would change or become less clear. You would no longer be clearly saying that the lesson starts late.

Repeating the verb helps keep the parallel structure:

• our meeting starts early
• but her lesson starts late

So the repetition is normal and useful here.

אבל means but.

It connects two contrasting ideas:

• הפגישה שלנו מתחילה מוקדם = Our meeting starts early
• השיעור שלה מתחיל מאוחר = her lesson starts late

So אבל introduces the contrast between early and late.

Yes—that is actually a helpful way to understand the structure.

It is not how natural English works, but it matches the Hebrew pattern well:

• הפגישה שלנו = literally the meeting of ours
• השיעור שלה = literally the lesson of hers

This can help English speakers get used to Hebrew word order in possessive phrases.