This story is about wthen first time I learned about tea manner for the first time.

When my friend and I visited his house, she used to treat us to green tea.

One day, she suggested us towe learn about the tea manner.

The tea, which (that) she gave us wereas excellent and full aromatic, so we had awere curious about the tea manner as well.

When I drink tea, I should use four fingers of my right hand forto holding a next of the cup.

I should use three fingers of my left hand forto supporting a the bottom of the cup.

I should not drink tea at a time.all the tea at once. (?)

This sentence is a little unclear, so I took a guess. :)

This experience was really left an impressed forion on me, so I can remindvividly remember the scene and the feeling.

If you (ever) have a chance, I recommend trying the tea manner.

Or: If you (ever) get a chance, I recommend trying the tea manner.

When my friend and I visited his house, she used to treat us to green tea.

One day, she suggested us tothat we should learn about the tea manner.

The tea, which that she gave us wereas excellent andwith a full aroma, soand we had awere curious about the tea manner as well.

When Iyou drink tea, I during tea manner, you should use four fingers of myour right hand forto holding a next the side of the cup.

I changed the pronoun here from "I" to "you", because even though this is your story, you are essentially instructing someone on how they would hold a cup during tea manner.

IYou should use three fingers of myour left hand forto supporting a the bottom of the cup.

IAnd, you should not drink tea at a timhe tea all at once.

I am not completely sure what you mean by "at a time".

Before drinking the tea at my friend's housea, I smell the teaed it.

Whilen drinking it, I could taste the tea, which has fivefive different flavors.

Shortened the sentence to sound more natural.
You could also add a colon (:) and mention some of the flavors you remember. For example, "I tasted many flavors: turmeric, orange, mint, and rose."

After swallowing it, I canould taste the remaining flavor in my mouth.

This experienceI was really impressed for mby the experience, so I can remindember the scene and themy feelings well.

If you have a chance, I recommend trying the tea manner.

Tea MannerEtiquette

This story is about when I learned about tea mannerhe etiquette of pouring tea for the first time.

My friend's mother was a master of the tea manneretiquette of pouring tea.

When my friend and I visited his house, she used to treatgive us green tea.

One day, she suggested us towe learn about the tea manneretiquette of pouring tea.

The tea, which she gave us wereas excellent and full of aroma, so we had abecame curious about the tea manner as well.

When I drink tea, I should use four fingers of my right hand forto holding a next of the cup.

I should use three fingers of my left hand forto supporting a the bottom of the cup.

I should not drink all tea at a timonce.

Before drinking tea, I should smell the tea.

When drinking it, I tasteshould savour the tea, which has five flavors.

This experience was really impressived for me, soand I can remindstill remember the scene and the my feeling.s.

If you have a chance, I highly recommend the tea manneretiquette of drinking tea.