Last week, an event to introduce Japanese culture to foreigners living in Japan was held as a part of a Japanese language class. Last week, an event to introduce Japanese culture to foreigners living in Japan was held as part of a Japanese language class.

Last week, an events a part of a Japanese language class an event was held in order to introduce Japanese culture to foreigners living in Japan was held as a part of a Japanese language class. Last week, as a part of a Japanese language class an event was held in order to introduce Japanese culture to foreigners living in Japan.

Last week, there was an event to introduceing Japanese culture to foreigners living in Japan was held as a part of a Japanese language class. Last week, there was an event introducing Japanese culture to foreigners in Japan as a part of a Japanese language class.

grammatically correct but this is smoother

I teachaught the class as a volunteer. I taught the class as a volunteer.

This event takes place a couple of times aeach year. This event takes place a couple of times each year.

"How's everything going there?" "How's everything going there?"

How's everything going there?" How's everything going there?"

On a letters, they pasted origami paper cut out in the patterns of a cherry blossom petals. On letters, they pasted origami paper cut out in patterns of cherry blossom petals.

On athe letters, they pasted origami paper cut out in the patterns of a cherry blossom petals. On the letters, they pasted origami paper cut out in patterns of a cherry blossom petals.

There are several foreigners, so there are several letters (unless there is only one letter that everybody is all pasting on, then only "letter" at the start is plural but all of them still pasted their own papers)

On a letter tThey pasted an origami paper cut out in the pattern of a cherry blossom petal on their letters. They pasted an origami paper cut out in the pattern of a cherry blossom petal on their letters.

Besides the pattern, they added messages to their family back home. Beside the pattern, they added messages to their family back home.

Besides the pattern, they added messages to their familyies back home. Besides the pattern, they added messages to their families back home.

"their family" implies they all are part of only one family informally you might be understood though but this is better

Besides the pattern, they added messages to their familyies back home. Besides the pattern, they added messages to their families back home.

Some foreigners lookedwere confused about not being able to use a Japanese brush properly. Some foreigners were confused about not being able to use a Japanese brush properly.

Some foreigners looked confused abouts to not being able to use a Japanese brush properly. Some foreigners looked confused as to not being able to use a Japanese brush properly.

GettFollowing the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come." Following the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come."

GettingWhen given the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come. When given the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come.

GettUsing the lecturer's advice, "The words to write oin theyour letter will come out spontaneously when you think of your family back home," each of them started to write, "Spring has come. Using the lecturer's advice, "The words to write in your letter will come out spontaneously when you think of your family back home," each of them started to write, "Spring has come.

"Getting" sounds awkward here

GettTaking the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come. Taking the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come.

"to take" + someone's + "advice"

GettTaking the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come. Taking the lecturer's advice, "The words to write on the letter will come out spontaneously when you think of your family back home," each of them started to write "Spring has come.

This time, we made a letter with pictures using Japanese brushes and ink. This time, we made a letter with pictures using Japanese brushes and ink.

This time, we made a letter with pictures using Japanese brushes and ink. This time, we made a letter with pictures using Japanese brushes and ink.

This time, we made a letter withs and drew pictures using Japanese brush and ink. This time, we made letters and drew pictures using Japanese brush and ink.

FThe foreigners who participated came from various countries including Vietnam, China, Bangladesh, and Finland. The foreigners who participated came from various countries including Vietnam, China, Bangladesh, and Finland.

or "I want to see you, maom." or "I want to see you, mom."

or "I want to see you, maum." or "I want to see you, mum."

or mom spelling depends on American/UK English

or "I want to see you, maom." or "I want to see you, mom."

or "I want to see you, maom/mum." or "I want to see you, mom/mum."

"Mam" sounds like "Ma'am" which is not how people call their mothers "Mom" = american english "Mum" = british english

or "I want to see you, maom." or "I want to see you, mom."

However, all of their characters were written hard with devotion to their family and seemed valuable to me. However, all of their characters were written hard with devotion to their family and seemed valuable to me.

However, all of their characters written hard with devofilled with consideration to their family seemed valuablesentimental to me. However, all of their characters filled with consideration to their family seemed sentimental to me.

However, all of their characters written hard withwith effort and devotion to their family seemed valuable to me. However, all of their characters written with effort and devotion to their family seemed valuable to me.

However, all of their characters, written hardtirelessly with devotion to their family, seemed valuable to me. However, all the characters, written tirelessly with devotion to their family, seemed valuable to me.

this is alright but I would say "all the characters" instead of "all of their characters" as this might be confusing with "character" meaning someone's personality/reputation. i would just say "the characters" since you already mentioned them writing kanji earlier. The commas are mandatory if you are writing as it's difficult to understand these kinds of sentence structures without the commas. "Hard" is also not very easy to understand (I had to read this twice to figure out what it meant) and this adverb is better

However, all of their characters were written hard with devotion to their familyies, which seemed valuable to me. However, all of their characters were written hard with devotion to their families, which seemed valuable to me.

I'm wondering whether they put them if they ended up posting the post box or ham or just placed them on display in their rooms. I wonder if they ended up posting them or just placed them on display in their rooms.

I'm wondering whether they put them in the post box or hadput them on display in their rooms. I wonder whether they put them in the post box or put them on display in their rooms.

Present tense is better than present continuous since "I'm wondering" implies you are wondering about it now as you are writing this. "to put + something + on display" set expression

I'm wondering whether they put them in the post box or hadve them on display in their rooms. I wonder whether they put them in the post box or have them on display in their rooms.

Anyway, I hope their hearts reach their familyies back home. Anyway, I hope their hearts reach their families back home.

Anyway, I hope their hearts reach their familyies back home. Anyway, I hope their hearts reach their families back home.

Some of the characters were either written in the wrong stroke order or were out of balance. Some of the characters were either written in the wrong stroke order or out of balance.