Iam wondering how to write a good introduction. What is needed in order to write a good introduction? How can i leave a good first impression on the examiner? Emotion: smile Is this a good introduction? Or is it too long? How can i shorten it? Is there any mistake?

Oh, do i need to leave a line and start a new paragraph when one person talks? Or can i combine it into the paragraph?
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“Hey, you are such an imbecile brat!” I called out to my little brother, “quiet down will you! I’m studying!”
“Oh, imbecile, is that a good word?” He stopped bouncing his basketball and looked at me.
“Yes, it is. Now, scram!” I waved him away.
“What does it mean?” He raised his eyebrow suspiciously.
“It means that you are a nice little boy. Now, stop bothering me!” I stared. My little brother nodded in agreement. Then, he turned his body around and screamed, “Mom! Sister called me an imbecile brat! I know it is a bad word!” I rolled my eyes, “Mom! She needs to be severely punished!” Fortunately, Mother ignored him. I am a sixteen-year-old teenage girl with short black hair. I am not a girl whom people considered as attractive. I have this irritating eight-year-old brother, Nat, who loves to disturb me, simply because he has got nothing else to do. Later that day, I figured out why Mother had been ignoring Nat. She was having her earphones on, listening to her favorite songs sang by Lionel Richie. What a clever Mother! I have this mother whom I consider as a hero. She is a very clever woman - clever at handling Nat.

While I was studying for my major exam in the afternoon, Mother suddenly appeared out of nowhere.
“Vanessa, I’ll be out for a while! Remember to look after Nat!” and Mother ran out of the house.
“Oh no, not babysitting him again!” I slapped my hand against my forehead. The last time I babysat Nat, he blasted the television screen into smithereens with his green metal ball.
“Nat Ong Yi Wei! You better not try anything funny this time!” Nat turned around with three fingers up.
“Cross my heart,” he smiled, showing his two little sharp rabbit teeth.
“I don’t believe you,” I returned to do my revision.

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Pleasecorrectme
What is needed in order to write a good introduction? - You need to arouse your readers' interest and plant enough clues in your intro. for your story

Oh, do i need to leave a line and start a new paragraph when one person talks? Or can i combine it into the paragraph? It depends.
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“Hey, you are such an imbecile brat!” I called out to my little brother, “quiet down will you! I’m studying!”
“Oh, imbecile, is that a good word?” He stopped bouncing his basketball and looked at me.
“Yes, it is. Now, scram!” I waved him away.
“What does it mean?” He raised his eyebrow suspiciously.
“It means that you are a nice little boy. Now, stop bothering me!” I stared. My little brother nodded in agreement. Then, he turned his body around and screamed, “Mom! Sister called me an imbecile brat! I know it is a bad word!” I rolled my eyes, “Mom! She needs to be severely punished!” (She is more likely to tell mom what the brother did to annoy her.) Fortunately, Mother was listening to Lionel Richie with her headphones and didn't hear what he said. I am a sixteen-year-old teenage girl with short black hair. I am not a girl whom people considered as attractive. (This does not belong here.)

I have this irritating eight-year-old brother, Nat, who loves to disturb me, simply because he has got nothing else to do. Later that day, I figured out why Mother had been ignoring Nat. She was having her earphones on, listening to her favorite songs sang by Lionel Richie. What a clever Mother! I have this mother whom I consider as a hero. She is a very clever woman - clever at handling Nat. (This is where you provide your long history of complaints against him.)

(The following isn't exactly an intro.)
While I was studying for my major exam in the one afternoon, Mother suddenly appeared out of nowhere.
“Vanessa, I’ll be out for a while! Remember to look after Nat!” and Mother ran out of the house.
“Oh no, not babysitting him again!” I slapped my hand against my forehead. The last time I babysat Nat, he blasted the television screen into smithereens with his green metal ball.
“Nat Ong Yi Wei! You better not try anything funny this time!” Nat turned around with three fingers up.
“Cross my heart,” he smiled, showing his two little sharp rabbit teeth.
“I don’t believe you,” I returned to do my revision.

I am abit confuse How should i organise the introduction? Where should i place the introduction of my character?

Example: I am a sixteen-year-old teenage girl with short black hair. I am not a girl whom people considered as attractive.

Where is the appropriate place for that sentence?
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Why is the narrator's appearance important to your story?

The teenage bit may be important though. You can bring it up indirectly. e.g. Mention how you need to study for a major university entrance exam, or have that brother call his sister an annoying 16-year-old (when appropriate).
Thank you so much for helping me!