4. MWhenever I spill my coffee is, I always spilled it on the keyborard.

In the end, I find this kind of Japanese men are full of almost all the tablesalmost all the tables are full of this kind of Japanese man that day.😩

1. Only when I go for drink with my friends even though my face is puffy and I feel a little sick because I went out drinking at the previous night, do I meet a nice and handsome bartender at a bar.

I throw up atin the bathroom later and he cleans thereit up.

Today I am summeding up my experiences that falling into Murphy's law.

1. When the company I work for announced tohat they would let us work from home due to the coronavirus probelms, I happily bought a lot of booze and finger food to enjoy them at home, but I ended up going to the office everyday for many reasons.

2. Only when I wear new clothes I splurged on to the office, do I spilled coffee and goet a big stain on them .

The "only when" construction requires inversion, using an auxiliary verb ("do," "will," "can," "have," "be," etc.). This page provides some examples and explanation: https://www.perfect-english-grammar.com/inversion.html

3. Only when I bought anice, expensive nice food for my lunch at a famous deldelicatessen shop before going to the office in the morning, did our boss tells us to go out for lunch on him.

4. My coffee is always spilleds on the keyborard.

This is technically correct, but here, you probably want to emphasize the action, using the active voice.

5. Only when I have to make documents immediately, will the computer is frofreezen and won't be unfixed soonable for a while.

"For a while" makes sense based on context, but you might want to use a different verb.

(Usually 4 to 5four to five attendees sit at a table and talk about a topic together. After 30 minutes, we change tables asper the event staff's instructions and talk about another topic with different attendees. )

Usually, unless you want to emphasize the number, like in a math problem, you should write out small numbers. The exact cut-off varies, but those less than 10 generally fall into that category. Example:
- Fyodor Pavlovich had three sons: Dmitri, Ivan, and Alexei.
- I have 5 apples. I give 3 to you. How many do I have now?

1. Only when I memorized many Engligsh phrases and I'mwhen I was pumped up for conversation in English, were the attendees at the first tabel are Japanesle middle-aged Japanese men who came there to find a playmate.

I still say merrily, "Hello!

Commas go before quoted speech, if the "I said" part is before the quote. Example:
- I said, "Don't walk on the ice!"
- "Don't walk on the ice!" I said.

", b But they just say "Are you married?

Normally, we don't really put a quote in the middle of a sentence: either it starts it or ends it. The part after the quote should be broken off.

In the end, I find this kind of Japanese men are full of almost all the tablesat all the tables are full of this kind of Japanese men that day.😩

2. Only wWhen I attend a language exchange event on the spur of the moment because my plan suddenly got cancelled and I want to just kill time by chatting with Japanese English learners, native English speakers are full of almost all the tablealmost all the tables are full of native English speakers.😆

The first part is a bit too long for the "only when" structure.

(Naturally I can't speak English as I dohaven't prepared any English phrase. )

"Don't" describes the situation in general, but based on (1), it sounds like you do normally prepare.

1. Only when I go for drink with my friends even though my face is puffy and I feel a little sick because I went out drinking at the previous night,. I meet a nice and handsome bartender at a bar.

This was a bit long, so I think it sounds better in two sentences.

I drink a nice cocktailk he made.

2. My hairstyle is always on point in the placewhen there are no people around.

3. When I'm on a roll, the shops and the events are all closed and cancelled.

"On a roll" doesn't quite work here. I don't know Japanese, so I'm not sure if it fits your original idea, but maybe something like "When I'm in a good mood" or "When I'm out and about" would work better.