بما أن الدورة المسائية في مستوى مبتدئ، يختارها المتدرب.

بما أن is a conjunction meaning since, because, or given that.

It introduces a reason:

• بما أن الدورة المسائية في مستوى مبتدئ = Since the evening course is at a beginner level...

A helpful way to think about it:

• أن = that
• بما أن as a whole functions like since / given that

In Modern Standard Arabic, بما أن is common when giving an explanation that leads to a result in the next clause.

This is a noun + adjective combination:

• الدورة = the course
• المسائية = evening / evening-time

In Arabic, adjectives usually come after the noun they describe, unlike in English.

So:

• الدورة المسائية literally = the course the-evening
• natural English order = the evening course

Also notice agreement:

• الدورة is feminine singular
• so the adjective المسائية must also be feminine singular

That is why it is المسائية, not المسائي.

Because it describes الدورة, and الدورة is a feminine noun.

Arabic adjectives must agree with the noun in:

• gender
• number
• definiteness

Here:

• الدورة = feminine singular definite
• المسائية = feminine singular definite

So the adjective matches perfectly.

Compare:

• الدورة المسائية = the evening course
• البرنامج المسائي = the evening program

Since برنامج is masculine, the adjective becomes المسائي.

This phrase literally means something like at a beginner level.

Breakdown:

• في = in / at
• مستوى = level
• مبتدئ = beginner

So the structure is:

• في مستوى مبتدئ = at a beginner level

A native English speaker may expect something like in a beginner level, but Arabic uses this kind of phrasing naturally.

Also, مبتدئ here is functioning like a descriptor of the level. You can think of it as:

• a beginner level

In smoother Arabic, you may also see:

• في مستوى المبتدئين
• على مستوى مبتدئ
• للمبتدئين

But the basic idea in this sentence is clear: the course is suitable for beginners.

Because the phrase is describing a type of level, not pointing to a specific one.

• مستوى مبتدئ = a beginner level
• المستوى المبتدئ would mean the beginner level

So the indefinite form makes sense here because the sentence is talking about the course being at beginner level in general.

This is similar to English:

• It is at beginner level not
• It is at the beginner level unless you mean a specific known level.

The ها is an attached object pronoun meaning her / it.

It refers back to الدورة:

• الدورة is feminine singular
• so the pronoun used for it is ها

Breakdown:

• يختار = he chooses
• ها = it
• يختارها = he chooses it

Since الدورة is grammatically feminine, Arabic uses the feminine object pronoun.

Because Arabic nouns have grammatical gender.

In Arabic:

• feminine singular nouns often take feminine pronouns
• masculine singular nouns take masculine pronouns

So even though English uses it for things, Arabic still distinguishes:

• feminine noun → ها
• masculine noun → ـه

Here:

• الدورة is feminine
• therefore: يختارها

This is grammatical gender, not biological gender.

Because Arabic often uses verb–subject word order.

So:

• يختارها المتدرب = the trainee chooses it

This order is very normal in Arabic.

You can also have subject–verb order:

• المتدرب يختارها

Both are possible, but the sentence you were given uses the common verbal-sentence pattern:

• verb + subject + object

In this sentence:

• يختارها = chooses it
• المتدرب = the trainee

In Arabic, the present tense often expresses:

• present actions
• habitual actions
• general truths
• what someone would normally do in a situation

Here, يختارها المتدرب does not necessarily mean one single action happening right now. It can mean:

• the trainee chooses it
• the trainee would choose it
• the trainee tends to choose it

So the present tense works well for a general statement based on the reason given in the first clause.

The subject is المتدرب.

Arabic often places the subject after the verb, so although يختارها comes first, the doer of the action is still المتدرب.

So the second clause is:

• يختارها المتدرب
• literally: chooses it the trainee
• natural English: the trainee chooses it

Yes, المتدرب is masculine singular.

For a female trainee, you would normally say:

• المتدربة

Then the clause would become:

• تختارها المتدربة

Notice two changes:

1. المتدرب → المتدربة
2. يختارها → تختارها

That is because the verb must agree with a feminine singular subject when the subject is explicit in this kind of sentence.

Even if short vowels are not written, the sentence has clear grammatical roles:

• بما أن = conjunction
• الدورة = subject of the first clause
• المسائية = adjective describing الدورة
• في مستوى مبتدئ = prepositional phrase describing the course
• يختارها = verb + object pronoun
• المتدرب = subject of the second clause

If fully vowelled, the main roles would be roughly:

• الدورةُ المسائيةُ = nominative subject phrase
• في مستوى مبتدئٍ = after a preposition, مستوى is genitive, and مبتدئٍ follows it
• المتدربُ = nominative subject of the verb

A learner does not need to pronounce all those endings in normal reading at first, but it helps to know the structure.

A careful pronunciation is approximately:

al-masā’iyyah

A few things to notice:

• the long ā sound in مسا
• the hamza sound before ي
• the ending -iyyah, common in many adjectives

So it is not just masaiya in one smooth syllable. There is a slight break from the hamza:

• ma-sā-ʾi-yya

Yes. Arabic allows some flexibility.

For example:

• المتدرب يختارها بما أن الدورة المسائية في مستوى مبتدئ
• بما أن الدورة المسائية في مستوى مبتدئ، المتدرب يختارها

But the original version is very natural in structure:

• reason first
• result second

That makes the logic easy to follow:

1. Since the evening course is at beginner level
2. the trainee chooses it

So the original order is a good model.

Yes—three very common Arabic patterns appear here:

1. Reason connector first

   • بما أن = since / because

2. Noun before adjective

   • الدورة المسائية = the evening course

3. Attached object pronoun

   • يختارها = chooses it

If you can recognize those three patterns, the sentence becomes much easier to parse.