اگر من مطمئن بودم که او در خانه است، الان به او زنگ میزدم.

Not here. In this sentence, بودم is part of a present unreal / counterfactual conditional pattern.

So اگر من مطمئن بودم literally looks like if I was sure, but the meaning is closer to:

• If I were sure
• If I knew for sure

This is similar to English using a past form for something unreal in the present: If I were sure, I would call him now.

So بودم does not mean the speaker is talking about a real past situation. It helps show that this is a hypothetical situation.

Because Persian often uses the past imperfective form to express the result of an unreal condition, especially in sentences like this.

So:

• زنگ می‌زدم = I would call / I’d be calling

In this sentence, it does not mean a repeated past action. It expresses the imagined result of the condition.

The full pattern is:

• اگر ... بودم ، ... می‌زدم

That corresponds to English:

• If ..., I would ...

So الان به او زنگ می‌زدم means I would call him now.

Because است refers to the person's situation right now: whether he is at home.

The sentence is hypothetical, but the embedded statement itself is about a present fact:

• مطمئن بودم که او در خانه است
• I were sure that he is at home

So the tense choice makes sense:

• بودم = part of the unreal conditional structure
• است = the person’s current location/state

In everyday speech, you may also hear هست instead of است:

• اگر مطمئن بودم که او در خانه هست، الان به او زنگ می‌زدم.

Both are understandable, though است is a bit more formal/written.

Yes. Very often they are omitted, because the verb already shows the person clearly.

So these are both natural:

• اگر من مطمئن بودم که او در خانه است، الان به او زنگ می‌زدم.
• اگر مطمئن بودم که در خانه است، الان بهش زنگ می‌زدم.

Why can they be omitted?

• بودم already tells you the subject is I
• است can often work without repeating او if the context is clear
• Persian commonly drops pronouns when they are understood

The version with pronouns is still fine; it can sound slightly more explicit or emphatic.

که introduces the content of what the speaker is sure about.

So:

• مطمئن بودم که او در خانه است
• I was/were sure that he is at home

It functions like English that in this kind of sentence.

Without که, the sentence would sound incomplete or much less natural in standard Persian after مطمئن بودن when a full clause follows.

In Persian, زنگ زدن is the normal expression for to call / to phone, and the person called is introduced with به.

So:

• به او زنگ زدن = to call him/her
• literally something like to ring to him/her

Examples:

• به دوستم زنگ زدم = I called my friend
• بهش زنگ بزن = Call him/her

So به is part of how this verb is used. English speakers often want a direct object without a preposition, but Persian does not usually do that with زنگ زدن.

Yes. That is very common in everyday Persian.

• به او = more formal, careful, or written
• بهش = more conversational

So a very natural spoken version would be:

• اگر مطمئن بودم که خونه‌ست، الان بهش زنگ می‌زدم.

Compared with the original sentence, that spoken version also uses more colloquial forms:

• خانه → خونه
• است → ـه / خونه‌ست
• به او → بهش

الان means now, and it helps show that the result is about the present moment.

So:

• اگر من مطمئن بودم ... الان به او زنگ می‌زدم
• If I were sure ..., I would call him now

Without الان, the sentence could still work, but الان makes the time reference much clearer. It tells you the speaker means:

• right now, in the current situation

It also reinforces that this is a present counterfactual, not just a vague hypothetical.

The Persian sentence matches the meaning of If I were sure... more closely, because it is counterfactual or hypothetical.

In natural English, many people say both:

• If I was sure...
• If I were sure...

But from a grammar-learning point of view, If I were sure, I would call him now is the closest equivalent.

So Persian اگر ... بودم ... می‌زدم often corresponds well to English If ... were ..., would ....

Yes, Persian word order is somewhat flexible, especially with adverbs like الان.

For example, these are all possible:

• اگر من مطمئن بودم که او در خانه است، الان به او زنگ می‌زدم.
• اگر من مطمئن بودم که او در خانه است، به او الان زنگ می‌زدم.
• الان اگر مطمئن بودم که او در خانه است، به او زنگ می‌زدم.

But the original order is very natural and clear.

A good default pattern is:

• اگر
  • condition, + result clause

That is probably the safest structure for learners.

می‌ is a prefix used here as part of the imperfective form.

So:

• زدم = I hit / I rang / I called
• می‌زدم = I was hitting / I used to hit / in this context, I would call

In careful writing, Persian usually writes this with a special non-joining character:

• می‌زدم

You may also see less careful spellings such as:

• میزدم

But می‌زدم is the standard spelling.

The same applies to many verbs:

• می‌رفتم
• می‌گفتم
• می‌خواستم

No, that would usually suggest a past unreal meaning, and this sentence is not mainly about that.

The clue is الان = now. The sentence is about a present hypothetical result:

• If I were sure he is at home, I would call him now.

If you wanted a past unreal meaning like If I had been sure..., I would have called..., Persian would normally use a different context and often a different structure, for example with a clearer past-time reference.

So this sentence is best understood as a present counterfactual, not a past one.

Yes. A common spoken version could be:

• اگه مطمئن بودم که خونه‌ست، الان بهش زنگ می‌زدم.

Changes:

• اگر → اگه
• خانه → خونه
• است → ـه / خونه‌ست
• به او → بهش

The original sentence is perfectly good and understandable, but it sounds more formal or neutral-written. The spoken version sounds more like everyday conversation.