هو يشارك صديقه الشطيرة والوجبة الخفيفة.

Yes. The verb يشارك already tells you the subject is he because it is third-person masculine singular.

So هو is not strictly necessary. It is often added for:

• emphasis,
• clarity,
• or contrast with someone else.

Both of these are possible:

• هو يشارك صديقه الشطيرة والوجبة الخفيفة
• يشارك صديقه الشطيرة والوجبة الخفيفة

The second one is still a complete sentence.

يشارك is the imperfect form of the verb شارك.

In English, this can correspond to:

• he shares
• he is sharing

The exact choice in English depends on context. Arabic often uses the same imperfect form for both a simple present and a present progressive meaning.

صديقه is made of:

• صديق = friend
• ـه = his

So صديقه means his friend.

In fully vowelled MSA here, it would be صديقَهُ because it is in the accusative in this sentence.

Also, because it has a possessive suffix (his), it is already definite. That is why you do not add ال to it.

Because the verb شارك can work this way in Arabic.

In this sentence, شارك takes:

• the person being shared with: صديقه
• the thing being shared: الشطيرة والوجبة الخفيفة

So Arabic can express the idea directly as:

• He shares his friend the sandwich and the snack structurally

But the natural English translation is:

• He shares the sandwich and the snack with his friend

So English uses with, but Arabic does not need it here.

That order matches a common pattern with شارك:

• شاركَ شخصًا شيئًا
• to share something with someone

So the sentence presents:

1. the person involved: صديقه
2. the things being shared: الشطيرة والوجبة الخفيفة

Arabic word order is somewhat flexible, but this order fits the verb well.

Because they are definite here: they refer to a specific sandwich and a specific snack/light meal, not just any sandwich or any snack.

So:

• الشطيرة = the sandwich
• الوجبة الخفيفة = the light meal / the snack

If they were indefinite, you would expect forms like:

• شطيرةً
• وجبةً خفيفةً

Because Arabic is expressing that idea as a noun + adjective phrase:

• وجبة = meal
• خفيفة = light

So literally it means the light meal, which is a common way to express snack.

This is also a good example of adjective agreement:

• وجبة is feminine singular
• خفيفة is also feminine singular
• both are definite because of ال

In Arabic, adjectives normally agree with the nouns they describe in:

• gender,
• number,
• case,
• and definiteness.

So because الوجبة is definite, the adjective must also be definite:

• الوجبة الخفيفة

Not:

• الوجبة خفيفة if you mean the light meal as one noun phrase

That version would instead sound like a sentence meaning the meal is light.

In fully vowelled MSA, the sentence would be:

هو يشاركُ صديقَهُ الشطيرةَ والوجبةَ الخفيفةَ

A simple breakdown:

• هو = subject
• يشاركُ = imperfect verb
• صديقَهُ = object
• الشطيرةَ = object
• الوجبةَ الخفيفةَ = object phrase, with the adjective matching the noun

Because the nouns after the verb are objects here, they are in the accusative.

No. شارك can also mean participate or take part, depending on context.

For example:

• يشارك في النشاط = he participates in the activity

But in your sentence, because the verb is followed by food items, the meaning is clearly share, not participate.

It is pronounced ash-shaṭīra, not al-shaṭīra.

That is because ش is a sun letter, so the ل of الـ is not pronounced separately. Instead, the following consonant is doubled in pronunciation.

So:

• الشطيرة → ash-shaṭīra

By contrast, in الوجبة, the و is a moon letter, so the ل is pronounced:

• al-wajba / al-wajbah