يتنزه صديقي بأحذية للمشي قرب البحيرة والجبل.

Because Arabic often prefers verb-first word order, especially in neutral statements.

• يتنزه صديقي... = a common VSO pattern (verb–subject–other parts)
• صديقي يتنزه... = also correct, but it gives slightly more prominence to my friend

So both are possible. The original sentence uses a very normal Arabic structure.

يتنزه is an imperfect verb (often called the present/future form in basic textbooks).

It tells you several things at once:

• يـ = he
• the form is 3rd person masculine singular
• the basic meaning is he takes a walk / he strolls / he goes for a walk

So in this sentence, يتنزه matches صديقي because صديقي is singular and masculine.

Because the verb already contains that information.

In Arabic, يتنزه already means he walks / he strolls.
Then صديقي is added to specify who that he is.

So Arabic does not need a separate pronoun like هو here.

• يتنزه = he strolls
• يتنزه صديقي = my friend strolls

If you added هو, it would usually be for emphasis or contrast, not because grammar requires it.

Because ـي here is the possessive suffix meaning my.

• صديق = friend
• صديقي = my friend

So this is an iḍāfa-like possessive construction with a suffix, not a separate word for my.

Also, even though صديقي is the subject of the sentence, you do not see a visible ـُ ending for nominative case, because the noun is attached to ياء المتكلم (my). The case is understood grammatically, even if it is not clearly shown in writing.

The preposition بـ often means with, by, or using.

Here it gives the idea of accompanying equipment or means:

• بأحذية = with shoes

So the phrase suggests something like:

• wearing shoes
• with walking shoes on
• using/wearing walking shoes

That said, many learners notice that this is not the most idiomatic way to talk about what someone is wearing. It is understandable, but Arabic often prefers a more explicit wording for clothing or footwear.

Because أحذية is the plural of حذاء.

• حذاء = shoe
• أحذية = shoes

Using the plural is natural here, just as English normally says shoes, not shoe, when talking about footwear in general.

So بأحذية للمشي means something like with walking shoes.

Because the sentence is not talking about a specific already-known set of shoes.

• بأحذيةٍ = with shoes / with some shoes
• بالأحذيةِ = with the shoes

In the original sentence, the idea is general: walking shoes, not the particular walking shoes we already mentioned.

Also, after the preposition بـ, the noun is genitive, so with full endings it would be:

• بِأَحْذِيَةٍ

للمشي means for walking.

This is a very common Arabic way to express purpose or function:

• أحذية للمشي = shoes for walking
• حقيبة للسفر = a bag for travel
• غرفة للنوم = a room for sleeping

Here:

• لـ = for
• المشي = walking (a verbal noun, or maṣdar)

So the phrase describes the type of shoes.

Because in Arabic, after لـ in purpose/function expressions, the verbal noun often appears with الـ.

So:

• للمشي = for walking

This sounds normal in MSA. You can think of it as referring to the activity walking in a general sense.

Also notice the spelling:

• لِ + الـمشي becomes لِلْمَشْيِ
• in normal writing: للمشي

قرب here works like near, but grammatically it is often analyzed as a noun/adverb of place rather than a simple preposition.

In practice, for a learner, it helps to understand it like this:

• قرب البحيرة = near the lake

More exactly:

• قربَ is functioning as an adverbial expression of place
• البحيرةِ is genitive after it

So it behaves very much like near in English, even if traditional Arabic grammar analyzes it a bit differently.

Because both nouns have الـ:

• البحيرة = the lake
• الجبل = the mountain

That usually means the speaker has specific places in mind, or that these places are already identifiable from context.

If you wanted the indefinite meaning near a lake and a mountain, you could say:

• قرب بحيرةٍ وجبلٍ

So the original sentence means near the lake and the mountain, not just any lake and mountain.

Because one governing word can apply to both nouns when they are joined by و (and).

So:

• قرب البحيرة والجبل = near the lake and the mountain

You do not need to repeat قرب.

Repeating it would be possible for emphasis or clarity, but it is not necessary.

Yes. The Arabic imperfect can cover several English ideas, depending on context.

So يتنزه صديقي could mean:

• My friend is taking a walk
• My friend takes walks
• My friend goes for a walk

Context tells you whether it is happening right now, regularly, or more generally.

A fully vocalized version would be:

يَتَنَزَّهُ صَدِيقِي بِأَحْذِيَةٍ لِلْمَشْيِ قُرْبَ الْبُحَيْرَةِ وَالْجَبَلِ.

Some useful points in that version:

• يَتَنَزَّهُ = nominative imperfect ending ـُ
• صَدِيقِي = subject, nominative in function
• بِأَحْذِيَةٍ = genitive after بـ
• لِلْمَشْيِ = genitive after لـ
• قُرْبَ = accusative adverbial expression
• الْبُحَيْرَةِ and الْجَبَلِ = genitive after قرب in this construction

It is understandable, but a native speaker might choose a more natural phrasing if the goal is to emphasize what the friend is wearing.

For example:

• يتنزه صديقي قرب البحيرة والجبل مرتديًا أحذيةً للمشي.
• يتنزه صديقي بالقرب من البحيرة والجبل وهو ينتعل أحذيةً للمشي.

These sound more idiomatic if you want to say my friend is taking a walk near the lake and the mountain wearing walking shoes.

So the original sentence is useful grammatically, but stylistically it is a little less natural than some alternatives.