من داشتم به بانک میرفتم که همکارم زنگ زد و درباره حساب ما سوال کرد.

داشتم می‌رفتم is the past progressive: it means I was going or I was in the middle of going.

• رفتم = I went
• می‌رفتم can mean I was going, but it can also mean I used to go or I would go, depending on context
• داشتم می‌رفتم makes the ongoing action especially clear

So in this sentence, داشتم می‌رفتم helps set up the background action that was interrupted by the phone call.

Here, که means something like when or and then suddenly.

In the pattern داشتم ... که ..., Persian often means:

I was doing X when Y happened.

So:

من داشتم به بانک می‌رفتم که همکارم زنگ زد
= I was going to the bank when my coworker called

This is not the same که that means that in other sentences.

Because به often marks the destination of movement.

So:

• به بانک رفتن = to go to the bank
• به خانه رفتن = to go home / to the house
• به مدرسه رفتن = to go to school

With verbs of motion like رفتن, به is very common.

Yes. The verb already shows the subject, so من is not strictly necessary.

• داشتم already means I was having / I was
• So داشتم به بانک می‌رفتم already tells us the subject is I

Persian often drops subject pronouns when they are clear from the verb.
Adding من can give a little extra emphasis, clarity, or a more natural sentence opening.

همکارم means my coworker.

It is made of:

• همکار = coworker / colleague
• -م = my

So:

• همکارم = my coworker
• دوستم = my friend
• کتابم = my book

You could also say همکارِ من, which also means my coworker, but همکارم is shorter and very common.

زنگ زدن is a very common Persian expression meaning to call / to phone.

Literally, it comes from the idea of ringing, but in everyday Persian it simply means to call.

So:

• به من زنگ زد = he/she called me
• دیروز زنگ زدم = I called yesterday

In your sentence, همکارم زنگ زد means my coworker called.
Persian often leaves out به من if it is obvious from context that the person called me.

This is a very common storytelling pattern in Persian.

• داشتم می‌رفتم gives the background ongoing action
• زنگ زد and سوال کرد describe the completed events that happened during that background action

So the structure is:

• ongoing situation: I was going to the bank
• interrupting event: my coworker called
• next completed event: and asked about our account

This is very similar to English:
I was going to the bank when my coworker called and asked about our account.

Because Persian is usually a verb-final language.

That means words like objects, adverbs, and prepositional phrases usually come before the verb.

So:

• درباره حساب ما = about our account
• سوال کرد = asked

Putting them together:

درباره حساب ما سوال کرد
literally = about our account asked

That is normal Persian word order.

Because حساب ما is not the direct object here. It is part of a prepositional phrase:

• درباره حساب ما = about our account

The marker را is used for direct objects, not for nouns that come after a preposition like درباره.

Compare:

• درباره حساب ما سوال کرد = asked about our account → no را
• حساب ما را بستند = they closed our account → را is used, because حساب ما is now a direct object

Great question. In normal Persian writing, short vowels are usually not written, so the ezafe is often invisible.

But in pronunciation, this part is read roughly as:

درباره‌ی حسابِ ما
darbāre-ye hesāb-e mā

So there are two links:

• درباره‌ی حساب
• حسابِ ما

In ordinary writing, you may not see the -e clearly written, but native speakers still pronounce it.

Yes, absolutely.

• سوال کرد = asked a question / asked
• پرسید = asked

A very natural alternative sentence would be:

من داشتم به بانک می‌رفتم که همکارم زنگ زد و درباره حساب ما پرسید.

Both are correct.
In everyday speech, پرسید is often a little more direct and common.

It is understandable, but in standard formal spelling it is usually written as:

می‌رفتم

with a half-space (called نیم‌فاصله) between می and the verb stem.

So:

• common informal typing: میرفتم
• standard formal writing: می‌رفتم

Both are widely seen, but می‌رفتم is the preferred written form.

Because Persian does not have a definite article exactly like English the.

So:

• بانک can mean bank or the bank
• حساب can mean account or the account

Context tells you which meaning is intended.
If Persian wants to say a/an, it can use یک.

So in this sentence, بانک is understood as the bank from context, even though there is no separate word for the.

Yes. A very natural version is:

داشتم به بانک می‌رفتم که همکارم زنگ زد و درباره حساب ما سوال کرد.

This still clearly means I was going to the bank when my coworker called and asked about our account, because داشتم shows first-person singular.

So:

• من داشتم ... = slightly more explicit
• داشتم ... = also correct and very natural

Both are acceptable.