يتعرق صديقي على جهاز المشي.

يتعرق is the non-past form of تعرّق and means he sweats, he is sweating, or he perspires.

In Modern Standard Arabic, this one form can cover both:

• a general/habitual meaning: he sweats
• an action happening now: he is sweating

So context tells you which English translation fits best.

The يـ at the beginning is the usual non-past marker for he in many Arabic verbs.

The next ت is not a separate pronoun marker. It is part of the verb pattern itself. The base verb is تعرّق and belongs to a derived pattern often called Form V. So:

• past: تعرّق
• non-past: يتعرّق

So يتعرق is one complete verb form, not ي + separate word.

That is very normal in MSA. A common neutral sentence order is:

• verb + subject + rest

So يتعرق صديقي is completely natural.

You can also say:

• صديقي يتعرق على جهاز المشي

That is also correct, but it puts more attention on my friend.

Because the verb already includes that information.

يتعرق already tells you the subject is:

• third person
• masculine
• singular

So Arabic usually does not need a separate pronoun like هو here. You would only add هو if you wanted extra emphasis or contrast.

صديقي means my friend.

It is made from:

• صديق = friend
• ـي = my

So Arabic often expresses possession by attaching a suffix directly to the noun, instead of using a separate word like my.

Because a noun with a possessive suffix is already definite.

So:

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

Once you add ـي for my, you do not add ال. You also do not use tanween with this form.

على means on or on top of.

With جهاز المشي because a person stands or runs on a treadmill, على is the natural preposition:

• على جهاز المشي = on the treadmill

Using في would not sound right here, because you are not inside the treadmill.

Literally, it means something like the machine/device of walking.

• جهاز = device, machine
• المشي = walking

Together, جهاز المشي is the standard Arabic term for treadmill.

In the phrase جهاز المشي, the two nouns form a construct phrase, often called an iḍāfa.

In this kind of phrase:

• the first noun usually does not take ال
• the second noun can be definite

So:

• not الجهاز المشي
• but جهاز المشي

Because المشي is definite, the whole phrase is understood as a definite expression: the treadmill.

A fully vowelled version is:

يَتَعَرَّقُ صَدِيقِي عَلَى جِهَازِ الْمَشْيِ

A simple pronunciation guide is:

yataʿarraqu sadiiqii ʿalaa jihaazi al-mashyi

A few notes:

• تعرّق has a doubled ر sound
• على is pronounced ʿalaa
• المشي begins with al- because م is not a sun letter

Because they are in the genitive.

• جهازِ is genitive because it comes after the preposition على
• المشيِ is also genitive because it is the second noun in the construct phrase جهاز المشي

So in full vowelled MSA:

• على جِهَازِ الْمَشْيِ

This is a good example of how prepositions affect case in Arabic.

Yes.

The form يتعرق can express either:

• a habitual action
• an action happening now

So both are possible translations. If you want to make right now clearer, Arabic often adds a time word such as الآن:

• يتعرق صديقي الآن على جهاز المشي = My friend is sweating on the treadmill now

Yes. That is correct too.

Compare the two:

• يتعرق صديقي على جهاز المشي = neutral, common MSA verb-first style
• صديقي يتعرق على جهاز المشي = also correct, with more focus on my friend

So the difference is mainly one of style and emphasis, not basic meaning.