بعد أن أكتب الرسالة، أقرأها على الشاشة مرة أخرى.

بعد أن means after when it introduces a whole clause. So بعد أن أكتب الرسالة means after I write the message/letter.

• بعد = after
• أن introduces the verb clause that follows

In MSA, this is a very common way to say after doing something.

Because Arabic verbs already include the subject.

• أكتب = I write
• أقرأ = I read

The prefix أ marks first person singular in the imperfect. A separate أنا is optional and is usually only added for emphasis or contrast.

In Arabic, the imperfect can express several ideas: present, habitual action, future, or a general sequence of actions. In this sentence, it can sound like a routine or process:

After I write the message, I read it again on the screen.

So the sentence is not necessarily about one finished past event. If you wanted a clearly completed past meaning, Arabic would normally use the perfect: بعد أن كتبتُ الرسالة، قرأتها على الشاشة مرة أخرى.

Yes. After أن, the imperfect verb is normally in the subjunctive. In fully vowelled Arabic, this would be:

أكتبَ

But short vowels are usually not written in normal Arabic text, so you just see أكتب. That means the spelling looks the same even though the grammatical case of the verb has changed.

أقرأها has two parts:

• أقرأ = I read
• ها = it

So أقرأها means I read it.

Arabic very often attaches object pronouns directly to the verb like this.

Because الرسالة is grammatically feminine. Arabic object pronouns must agree with the grammatical gender of the noun they refer to.

• الرسالة is feminine, so it becomes ها
• If the noun were masculine, you would use ه

For example:

• أقرأ الرسالة → أقرأها
• أقرأ الكتاب → أقرأه

على الشاشة means on the screen.

Arabic often uses على for something appearing on a surface or display, so on the screen is very natural as على الشاشة. Here it tells you where the message is being read.

Literally, مرة أخرى is something like another time or one more time. Naturally, it means:

again
or
once again

It is one of the most common MSA expressions for again.

It can mean either, depending on context.

• In a more traditional or formal context, الرسالة can mean letter
• In modern everyday usage, it can also mean message

Since this sentence says على الشاشة, message may feel especially natural here, but letter is still possible depending on the situation.

You would normally use the perfect tense:

بعد أن كتبتُ الرسالة، قرأتها على الشاشة مرة أخرى.

That means After I wrote the message, I read it again on the screen.

So the original sentence with imperfect verbs sounds more like a routine, a procedure, or something not tied to a single completed past event.

Yes, بعدما can also mean after before a clause, and you will see it in Arabic. But بعد أن is a very clear and standard MSA choice.

So both patterns exist, but بعد أن is especially useful for learners because it is straightforward and very common in formal Arabic.