يخمن صديقي الرمز السري ويفتش درج المكتب.

يخمن is the imperfect verb form, which often corresponds to the English present. Here it can mean guesses or is guessing, depending on context.

So يخمن صديقي can mean:

• My friend guesses
• My friend is guessing

Arabic imperfect verbs can also sometimes refer to the future, but that is not the most natural reading here.

Arabic verbs already show the subject inside the verb itself.

In يخمن, the prefix يـ tells you the verb is 3rd person masculine singular: he guesses / he is guessing.

So Arabic does not need a separate pronoun like he unless there is a special reason to add it for emphasis or contrast.

Because verb–subject–object order is very common in Arabic.

So:

• يخمن صديقي الرمز السري = My friend guesses the secret code

Arabic could also say:

• صديقي يخمن الرمز السري

That version is also correct, but it starts with the subject instead. Very roughly:

• يخمن صديقي... = a normal verbal sentence
• صديقي يخمن... = puts a bit more focus on my friend

صديقي breaks down as:

• صديق = friend
• ـي = my

So صديقي means my friend.

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

Because nouns with possessive suffixes do not normally take الـ.

So:

• صديق = a friend
• الصديق = the friend
• صديقي = my friend

Once the noun has ـي meaning my, it is already definite, so الـ is not used.

Because السري is an adjective describing الرمز, and in Arabic adjectives agree with the nouns they describe in definiteness.

So:

• رمز سري = a secret code
• الرمز السري = the secret code

Both words take الـ because the whole phrase is definite.

Because these are two different structures:

1. الرمز السري = noun + adjective

   • الرمز = the code
   • السري = secret
     The adjective matches the noun.

2. درج المكتب = noun + noun in an iḍāfa construction

   • literally: drawer of the desk/office

So الرمز السري is descriptive, while درج المكتب shows possession or close relationship.

Because it is the first noun in an iḍāfa construction.

In an iḍāfa:

• the first noun usually does not take الـ
• the second noun determines whether the whole phrase is definite

So:

• درج مكتب = a desk drawer / an office drawer
• درج المكتب = the desk drawer / the office drawer

Even though درج has no الـ, the whole phrase is definite because المكتب is definite.

It can mean either one, depending on context.

So درج المكتب could literally be understood as:

• the desk drawer
• the office drawer

In many learning sentences, it is often taken as desk drawer, but context is what decides.

Because of sun letters and moon letters.

In this sentence:

• الرمز is pronounced ar-ramz because ر is a sun letter
• السري is pronounced as-sirrī because س is a sun letter
• المكتب is pronounced al-maktab because م is a moon letter

So the spelling keeps الـ, but the pronunciation changes depending on the next letter.

Because the subject is understood to be the same.

ويفتش means and he searches / and he is searching. Since the verb is again 3rd person masculine singular, Arabic does not need to repeat صديقي.

So the sentence works like this:

• يخمن صديقي الرمز السري = My friend guesses the secret code
• ويفتش درج المكتب = and searches the desk drawer

English often repeats the subject less than beginners expect too, but Arabic does this very naturally.

Yes. Normal Arabic writing usually leaves out most short vowels and often other diacritics too.

So these verbs are understood as:

• يُخَمِّنُ
• يُفَتِّشُ

Both have a doubled middle consonant, but that doubling is not shown in the plain spelling here.

A more fully vocalized version of the sentence would be:

يُخَمِّنُ صَدِيقِي الرَّمْزَ السِّرِّيَّ وَيُفَتِّشُ دُرْجَ الْمَكْتَبِ

Learners often find this surprising at first, because Arabic usually expects readers to supply those details from context and vocabulary knowledge.