من وقتی به ساختمان رسیدم، داشتم آدرس و شماره را دوباره میخواندم تا طبقه سوم را پیدا کنم.

Yes—من is often optional here.

Because رسیدم and داشتم already show I through their endings, the sentence could naturally be:

وقتی به ساختمان رسیدم، داشتم آدرس و شماره را دوباره می‌خواندم تا طبقه سوم را پیدا کنم.

Including من adds a little emphasis or clarity, but it is not required.

وقتی means when.

It introduces a time clause:

• وقتی به ساختمان رسیدم = when I arrived at the building

So the sentence is structured like:

• When I arrived at the building, I was rereading the address and number so that I could find the third floor.

The verb رسیدن usually goes with به when it means to arrive/reach.

So:

• به ساختمان رسیدم = I arrived at the building
• literally: I reached to the building

This is just the normal pattern of the verb in Persian.

Other examples:

• به خانه رسیدم = I arrived home / at the house
• به مدرسه رسیدیم = we arrived at school

رسیدم is the simple past of رسیدن.

Breakdown:

• رسید- = past stem
• -م = I

So:

• رسیدم = I arrived

In this sentence, it marks the completed action in the when clause:

• when I arrived at the building

داشتم ... می‌خواندم is a more explicit past progressive structure: I was reading.

• داشتم = I was having / I was in the process of...
• می‌خواندم = I was reading / I read

Together:

• داشتم می‌خواندم = I was reading

This is very common in spoken and written Persian when you want to stress that an action was ongoing at that moment.

So:

• وقتی رسیدم، داشتم می‌خواندم = When I arrived, I was reading

Using just می‌خواندم can also work in many contexts, but داشتم ... می‌خواندم makes the progressive meaning clearer.

Good question. Both can often translate as I was reading, but they are not always identical in feel.

• می‌خواندم can mean I was reading or I used to read, depending on context.
• داشتم می‌خواندم specifically emphasizes an action that was in progress at that moment.

So here, since the sentence describes what was happening when the speaker arrived, داشتم می‌خواندم is especially natural.

Yes, the more standard spelling is:

• می‌خواندم

with a half-space / zero-width non-joiner between می and the verb.

Many people type it without that half-space:

• میخواندم

Both are understood, but می‌خواندم is the standard written form.

Also note the pronunciation:

• می‌خواندم is pronounced roughly mikhândam
• even though it looks like it contains خوان, in speech the و is not pronounced as an English w

را marks the direct object.

Here, the thing being reread is:

• آدرس و شماره = the address and number

So:

• آدرس و شماره را می‌خواندم = I was reading/rereading the address and number

Even though there are two nouns joined by و, they form one coordinated object, and را comes after the whole phrase.

Compare:

• کتاب را خواندم = I read the book
• کتاب و مجله را خواندم = I read the book and the magazine

شماره literally means number, but in context it can mean different things:

• street number
• apartment/unit number
• building number
• room number

So آدرس و شماره means something like the address and the number, where the exact type of number depends on the situation.

It sounds natural in context, especially if the speaker is trying to locate a place inside or around a building.

دوباره means again or once again.

Here:

• دوباره می‌خواندم = I was reading again / rereading

Persian adverbs like دوباره are fairly flexible, but its placement before the main verb is very natural.

So:

• آدرس و شماره را دوباره می‌خواندم = I was rereading the address and number

Here تا means so that / in order to.

It introduces a purpose clause:

• تا طبقه سوم را پیدا کنم = so that I could find the third floor

So the speaker rereads the address and number for a purpose:

• to find the third floor

This is a very common Persian pattern:

• ... تا + subjunctive verb

Examples:

• رفتم تا او را ببینم = I went to see him
• پرسیدم تا مطمئن شوم = I asked so that I could be sure

Because after تا meaning so that / in order to, Persian normally uses the subjunctive.

So:

• پیدا کنم = that I find / so that I can find

In this sentence, it is best understood as:

• so that I could find the third floor

This is the expected grammar after تا in a purpose clause.

Compare:

• می‌کنم = I do / I am doing
• کردم = I did
• کنم = I do / may do / can do in a subjunctive-type context

In Persian, the noun usually comes first, and the ordinal number comes after it.

So:

• طبقه سوم = literally floor third
• natural English: the third floor

This is completely normal in Persian.

More examples:

• روز اول = the first day
• فصل دوم = the second chapter/season
• اتاق پنجم = the fifth room

Because طبقه سوم is the direct object of پیدا کنم.

So:

• طبقه سوم را پیدا کنم = find the third floor

Again, را marks the specific direct object.

Without going too deep, را often appears when the object is definite or specific, and here the third floor is specific.

Yes. پیدا کردن means to find.

It is a compound verb:

• پیدا = found, visible, apparent
• کردن = to do

Together:

• پیدا کردن = to find

Very common examples:

• کلیدم را پیدا کردم = I found my key
• راه را پیدا نمی‌کنم = I can’t find the way
• دوستم را پیدا کردم = I found my friend

It has three main parts:

1. من وقتی به ساختمان رسیدم

   • I, when I arrived at the building

2. داشتم آدرس و شماره را دوباره می‌خواندم

   • was rereading the address and number

3. تا طبقه سوم را پیدا کنم

   • so that I could find the third floor

So the overall pattern is:

• [time clause] + [main ongoing action] + [purpose clause]

That makes it a very useful model sentence for learners.

Yes, it is natural and understandable.

A slightly more standard written version would be:

من وقتی به ساختمان رسیدم، داشتم آدرس و شماره را دوباره می‌خواندم تا طبقهٔ سوم را پیدا کنم.

Possible minor notes:

• می‌خواندم is the standard spelling.
• In careful writing, some people write طبقهٔ سوم with the ezafe marker, though it is often omitted in everyday typing.

But the original sentence is perfectly understandable and quite natural.

In everyday speech, a speaker might drop من and pronounce things a bit more smoothly:

وقتی به ساختمون رسیدم، داشتم آدرس و شماره رو دوباره می‌خوندم تا طبقه سوم رو پیدا کنم.

Common spoken changes:

• ساختمان → ساختمون
• را → رو
• می‌خواندم → in speech, something like می‌خوندم

This is very common in colloquial Persian, though the original sentence is closer to standard written style.