For a long time, Japanese people have had nice custom called " 年賀状 ", which is a greeting card for the New Year.

However, these days, the custom is decreasing becoursause we already have found easier way to say greetings － e mail or social media.

But I don't know all of my old friend’s' account ofs for social media.

If you have multiple friends, the apostrophe goes after the "s".

So I usually write several cards for them, —not so muchthat many, though.

PreviousThe end of thelast year, I recieived a card from my old friend's husband.

It said, " As we are in mourning, we are not sending New Years card this year".

Exchanging greeting cards have a meaning of " I'm alive " or '' I'm doing well- being"." for our generation.

Handwriting letters is sometimes annoying.

If I send you a card, wouldo you write me back?

For a long time, Japanese havepeople have had a nice custom called " 年賀状 (nengajou) " which is a greeting card for the New Year.

"Japanese can be used as a noun to refer to 日本人, but it is more polite and respectful to refer to them as "Japanese people" because it reinforces the fact that you're talking about people.

However, these days, the custom is decreasing becoursying out because we already have found an easier way to say greetings － e each other － i.e via e-mail or social media.

Off course, I also use some gadgets just like you.

But I don't know all of my old friend’s account ofs' social media accounts.

Using nouns as modifiers in English is...challenging so I wanted to change it so it sounded more natural. Also! when you use an apostrophe with a plural noun, you put the apostrophe at the end of the word after the "s"
example: if it's one chair, then it's "the chair's leg" and if there are multiple chairs, you would say "the chairs' legs".
Since, you're talking about more than one friend, I moved the apostrophe to the end of the word after the "s" :)

So I usually write several cards for them all, but in reality, not so muchany, though.

PreviousAt the end of thelast year, I recieved a card from my old friend's husband.

It said, " As we are in mouning, we arewill not be sending a New Years card this year".

Actually, I didn't know the fact that my friend had passed away.

Exchanging greeting cards haves a meaning of " I'm alive " or '' I'm doing well- being"." for our generation.

watch the spacing when you use quotation marks :)
the open quote should start right after the quotation marks without a space and should end without a space between the last character and the end quotation marks

HandwWriting things out by hand is sometimes annoying.

If I sendt you a card, wouldo you write me back?

technically the "grammatically correct" way of saying this sentence is "If I were to send you a card, would you write me back?" but I changed it to the more colloquial way of saying it :)

Or is it troublesomwould it just be a hassle for you?

For a long time, the Japanese have had a nice custom called " 年賀状 " which is a greeting card for the New Year.

You can also say "Japanese people" instead of "the Japanese".

However, these days, the custom is decreasing becours we alreadyin popularity because we have found easier ways to say greetings － e mail or social media.

"Decreasing" is very general. Here are some more specific phrases you could use for talking about cultural customs: "falling out of fashion", "becoming less and less common", "becoming outdated".

Off course, I use sothe same gadgets likeas you.

I'm guessing by "gadgets" you probably meant something like cell phones, internet, technology, etc.

But I don't know all of my old friend’s account ofs' social media accounts.

So I usually write several cards for them, not so much, though.

By "not so much, though" did you mean "not so much anymore"? It's a little unclear.

PreviousAt the end of thelast year, I recieived a card from my old friend's husband.

It said, " As we are in mourning, we are not sending New Years cards this year".

Actually, I didn't know the fact that my friend had passed away.

Oh, no.

The phrase "oh no" is kind of lighthearted. It often is used for humorous situations. In the context of someone's death, it can be seen as insensitive. I would not recommend saying it unless you actually don't care, or if you are being sarcastic because you didn't like the deceased person.

I noticed.

I'm not sure what you were trying to say here. What did you notice? Or is it supposed to be part of the next sentence?

Exchanging greeting cards have a meaning of " is a way of saying "I'm alive " or '' I'm doing well- being"." for our generation.

But it's important to keep in touch.

I would link this with the previous sentence using a comma:

"Handwriting is sometimes annoying, but it's important to keep in touch."

If I send you a card, do you write me back?

Or is it too troublesome for you?

For long time, Japanese have had a nice custom called " 年賀状 " which is a greeting card for New Year's.

However, these days, the custom is decreasing becours we alreadyause we have found easier ways to say greetings － e -mail or social media.

Off course, I use some gadgets like you.

But I don't know all of my old friend’s account ofs' social media accounts.

So I usually write several cards for them, not stoo muchany, though.

PreviousAt the end of thelast year, I recieived a card from my old friend's husband.

It said, " As we are in mourning, we are not sending a New Year's card this year".

AI actually, I didn't know the fact that my friend had passed away.

Exchanging greeting cards haveconveys a meaning of " I'm alive " or '' I'm in well- being"." for our generation.

Or is it too troublesome for you?