يستكشف صديقي المحمية الطبيعية.

Because Arabic often allows a verb-subject-object order, especially in straightforward statements.

So this sentence is literally structured like:

• يستكشف = explores / is exploring
• صديقي = my friend
• المحمية الطبيعية = the nature reserve

This is a very normal Arabic sentence pattern. You could also put the subject first for emphasis:

• صديقي يستكشف المحمية الطبيعية.

That would still be correct, but the original verb-first order is especially common in Modern Standard Arabic.

يستكشف is in the imperfect form, which often covers:

• explores
• is exploring
• does explore
• sometimes even future meaning with context or a future marker

In this sentence, depending on context, it could mean either:

• My friend explores the nature reserve
• My friend is exploring the nature reserve

Arabic does not always separate simple present and present continuous as strictly as English does.

The form يستكشف begins with يـ, which commonly marks third person masculine singular in the imperfect.

So it means:

• he explores
• he is exploring

That matches صديقي because friend here is masculine singular.

If the subject were feminine, the verb would usually be:

• تستكشف = she explores / is exploring

صديقي means my friend.

It is made of:

• صديق = friend
• ـي = my

So:

• صديق = a friend / friend
• صديقي = my friend

The ـي is a possessive suffix attached directly to the noun.

Also, because this noun is possessed, it does not take الـ. Arabic normally does not say الصديقي for my friend.

Because possession already makes the noun definite.

In English, my friend is definite even though it does not use the. Arabic works similarly here.

So:

• صديق = a friend
• صديقي = my friend

Once the possessive suffix ـي is attached, the noun is already specific and definite, so الـ is not used.

Because this is a noun followed by an adjective, and in Arabic the adjective agrees with the noun in definiteness.

• المحمية = the reserve / the protected area
• الطبيعية = natural

Since the noun is definite, the adjective must also be definite:

• المحمية الطبيعية = the natural reserve / the nature reserve

If the noun were indefinite, the adjective would also be indefinite:

• محمية طبيعية = a natural reserve

This matching is a very important Arabic pattern.

Because adjectives normally come after the noun in Arabic.

So:

• المحمية الطبيعية = literally the reserve natural

But in good English, we translate it as:

• the natural reserve
• the nature reserve

This is one of the biggest word-order differences between English and Arabic.

Because محمية is a feminine noun, and the adjective must match it.

You can see the feminine ending ة on both words:

• المحمية
• الطبيعية

In Arabic, adjectives agree with the noun in:

• gender
• number
• definiteness
• case

So if the noun is feminine singular definite, the adjective must also be feminine singular definite.

The basic idea of محمية comes from a root related to protection, so yes, there is an underlying sense of something protected.

But as a vocabulary item, المحمية الطبيعية is the normal expression for:

• the nature reserve
• the natural reserve
• the wildlife reserve in some contexts

So although the literal pieces help, it is best learned as a set phrase meaning nature reserve.

Yes, in full formal Arabic there are case endings, although they are usually not written in ordinary text.

A fully vocalized version would be:

• يستكشفُ صديقي المحميةَ الطبيعيةَ.

Here:

• يستكشفُ ends with ـُ
• صديقي is the subject, so it is nominative in function
• المحميةَ is the direct object, so it takes the accusative
• الطبيعيةَ matches المحميةَ, so it is also accusative

In most everyday printed Arabic, these endings are omitted, so learners usually read the sentence without them.

A common Modern Standard Arabic way to negate the present meaning is with لا:

• لا يستكشف صديقي المحمية الطبيعية.
• My friend is not exploring the nature reserve / My friend does not explore the nature reserve

If you wanted past negation, you would use a different structure, such as:

• لم يستكشف صديقي المحمية الطبيعية.
• My friend did not explore the nature reserve

So the negation word depends on the time reference and style.