وقتی درس را نمیفهمم، از استادم سوال میکنم.

وقتی introduces a time clause. It can mean when or whenever, depending on context.

In this sentence, because both verbs are in the present tense and the idea is something that happens as a habit, the sense is often whenever:

• وقتی درس را نمی‌فهمم، از استادم سوال می‌کنم.

So the sentence is not just about one single moment. It usually describes a repeated or typical action.

Persian often leaves out subject pronouns when they are already clear from the verb ending.

Here:

• نمی‌فهمم = I don't understand
• می‌کنم = I do

The ending -م shows the subject is I, so من is not necessary.

You could say من وقتی... for emphasis, but it is usually omitted.

را marks the direct object, especially when it is specific or known.

So in:

• درس را نمی‌فهمم

the word درس is the thing being understood, and را marks it as the object.

A native English speaker often wants to translate را as a separate word, but it usually does not have a direct English equivalent. It is more of a grammar marker.

Very roughly:

• درس را = the lesson / the material as the object of the verb

Sometimes in casual Persian, object markers are omitted more than in careful standard Persian, but in a normal standard sentence like this, را is natural and expected.

With درس را, the lesson is treated as specific: the lesson/material being discussed.

If you remove را and say وقتی درس نمی‌فهمم..., it sounds less standard and can feel incomplete or colloquial.

So for learners, it is best to keep را here.

نمی‌فهمم breaks down like this:

• نـ = negation, not
• می‌ = present/imperfective marker
• فهم = verb stem related to understanding
• ـم = I

So:

• می‌فهمم = I understand
• نمی‌فهمم = I do not understand

This is a very common Persian pattern.

It looks the same, but it does two different jobs.

In نمی‌فهمم:

• -م is a verb ending
• it means I

In استادم:

• -م is a possessive ending
• it means my

So:

• نمی‌فهمم = I don't understand
• استادم = my professor / my teacher

Same sound, different grammar.

With the expression سوال کردن, Persian commonly uses از for the person you ask:

• از کسی سوال کردن = to ask someone a question

So literally, Persian structures it more like:

• to do a question from someone

but in natural English, you simply say:

• to ask someone

This is very common in Persian: the person involved is often introduced with a preposition where English would use a direct object.

Because سوال کردن is a common compound verb in Persian.

It is made of:

• سوال = question
• کردن = to do

So:

• سوال می‌کنم literally looks like I do a question
• but it actually means I ask a question

Persian uses many compound verbs like this.

A very common alternative is:

• از استادم سوال می‌پرسم

using پرسیدن / to ask.

Both are natural.

Both are natural, but they feel slightly different in style.

• سوال می‌کنم is very common in everyday Persian.
• سوال می‌پرسم is also very common and may feel a little more directly tied to the idea of asking.

Learners should understand both:

• از استادم سوال می‌کنم
• از استادم سوال می‌پرسم

Both work well in this sentence.

In Persian, the present tense often expresses habitual or repeated actions, not only what is happening right now.

So here:

• نمی‌فهمم = I don’t understand
• سوال می‌کنم = I ask

Together they mean something like:

• Whenever I don’t understand the lesson, I ask my teacher a question

So this is a general habit, not necessarily something happening at this exact moment.

Persian is generally a verb-final language.

That means the verb usually comes at the end of its clause.

Here the first clause is:

• وقتی درس را نمی‌فهمم
• literally: when the lesson OBJ I-don’t-understand

The second clause is:

• از استادم سوال می‌کنم
• literally: from my teacher question I-do

This verb-final order is one of the biggest differences from English.

The comma is helpful, but not always absolutely required.

In this sentence, it separates the time clause from the main clause:

• وقتی درس را نمی‌فهمم، از استادم سوال می‌کنم.

This is similar to English, where a comma is often used after an opening clause like When I don't understand the lesson, ...

So the comma is good style here.

In standard Persian spelling, these are usually written with a half-space:

• نمی‌فهمم
• می‌کنم

Many people type them without the half-space in casual writing:

• نمیفهمم
• میکنم

You may also see:

• سؤال instead of سوال

So a more standard written version of the full sentence is:

• وقتی درس را نمی‌فهمم، از استادم سؤال می‌کنم.

But the version without half-spaces is very common in informal typing.

استاد can mean professor, teacher, instructor, or even master/expert, depending on context.

In many learning contexts, استاد sounds like:

• professor
• instructor
• a respectful teacher

If you were talking about a schoolteacher, معلم might also be common.

So:

• استادم = my teacher / my professor / my instructor

The exact English choice depends on the situation.

درس can mean several related things:

• lesson
• class material
• subject matter
• sometimes even coursework

In this sentence, it usually refers to the material being taught, not necessarily the physical classroom period itself.

So a learner should understand it as something like:

• the lesson
• the material
• what is being taught

The best English choice depends on the context already given.