I wonder why onlySMOOTHER: Although I cmanage to read my messy letters in spitescrawl, it's very hard to read for other peoples to read. SMOOTHER: Although I manage to read my messy scrawl, it's very hard to read for others to read.

I wonder why only I can read my messy letters in despite it'sthem being very hard to read for other people. I wonder why only I can read my messy letters despite them being very hard to read for other people.

Mind the grammatical number. "Letters" is plural, so you should use "them".

I wonder why only II am the only one who can read my messy letters in spite ihandwriting. It's very hard to read for other people. I wonder why I am the only one who can read my messy handwriting. It's very hard to read for other people.

I wonder why only I can read my messy letters in despite it's being very hard to read for other people (to read?). I wonder why only I can read my messy letters despite it being very hard to read for other people (to read?).

I wonder why only I can read my messy letters in spite it's very hard to read'm the only person who can read my messy handwriting. It's much harder for other people. I wonder why only I'm the only person who can read my messy handwriting. It's much harder for other people.

I wonder why only I can read my messy letters in spitewhen it'’s very hard to read for other people. I wonder why only I can read my messy letters when it’s very hard to read for other people.

My way of pen grip might be a little strange/unusual. My pen grip might be a little strange/unusual.

MyThe way of pen gripI grip the pen might be a little strange. The way I grip the pen might be a little strange.

You can also say "my pen grip", but I personally prefer "the way I grip the pen".

My way of pen gripping the pen might be a little strange. My way of gripping the pen might be a little strange.

My way ofI think my pen grip might be a little strange. I think my pen grip might be a little strange.

My way of pen gripping the pen might be a little strange. My way of gripping the pen might be a little strange.

The opportunity to write has reduced these days because of computersSMOOTHER: With the advent of computers, fewer and fewer people write by hand. SMOOTHER: With the advent of computers, fewer and fewer people write by hand.

The number of opportunityies to write has reduced these days because of computers. The number of opportunities to write has reduced these days because of computers.

(1) Opportunities can't be "reduced", but the NUMBER of opportunities can. (2) You're talking about opportunities in general, rather than one specific opportunity, so the plural form ("opportunities") is expected.

These days, I have fewer opportunityies to write has reduced these days because of computers. These days, I have fewer opportunities to write because of computers.

The opportunity to write has reduced these daysIt's getting more and more uncommon to write because of computers. becoming popular. It's getting more and more uncommon to write because of computers becoming popular.

I think the appearance of Japanese language is coolOPTION A (with British spelling): However, I am fond of the aesthetics of Japanese scrips. OPTION B (with American spelling): However, I admire the esthetics of Japanese writing. OPTION A (with British spelling): However, I am fond of the aesthetics of Japanese scrips. OPTION B (with American spelling): However, I admire the esthetics of Japanese writing.

I think the appearance of the Japanese language is cool. I think the appearance of the Japanese language is cool.

We will either say "the Japanese language" (with the "the") or just "Japanese", nothing in between.

I think the appearance of Japanese languagescript is cool. I think the appearance of Japanese script is cool.

Language means the words/the language in general, script more specifically refers to the written language

I think the appearance of Japanese language ilooks cool. I think Japanese language looks cool.

I think the appearance of Japanese language is cool. I think the appearance of Japanese language is cool.

Do you mean written Japanese looks cool? A more natural way to say that may be “I think Japanese just looks cool.” or “I think Japanese as a language looks cool.”