Paid Holiday

I had four consecutive days off from last Friday.
I took paid holidays on last Friday and this Monday.
I went on a trip with my family to see my grandparents.
In Japan it is hard to ask for a paid holiday.
There are some reasons.
One of them is an old-fashioned idea about a promotion.
According to a survey, there is a correlation between a rate of promotion and working hours.
It says that people who do not take any paid holiday and work overtime, tend to get a promotion.
So most of the people* in Japan do not take a paid holiday.
As mentioned above, I can take a paid holiday without hesitation because not only my boss but also my coworkers in my department often take a paid holiday.

[* Or: "most people".]

Paid Holiday

I had a four consecutive days off from since last Friday.  (less formal: I had four days off in a row starting on Friday.)
I took paid holidays on last Friday and this Monday.
I went on a trip with my family to see my grandparents.  Grandparents is one word.
In Japan it is hard to ask for a paid holiday. (Paid holiday is fine. In American English you'd probably say "it is hard to ask for paid time off", but either is fine)
There are some reasons.  (This is correct but sounds a little incomplete.  "There are some reasons for this" is better)
One of them is an old-fashioned idea about a promotion. (OK. But I might say "...about promotions". A better sentence might be "There are some old-fashioned ideas around [career advancement / promotions] )
According to a survey, there is a correlation between a  the rate of promotion (or promotion rate) and working hours.
It says that people who does  do not take any paid holiday and works overtime tends to get a promotion.  (The word "people" is plural. So "people DO not... people TEND to get. More fluently: It says that people who do not take paid holidays and work overtime are promoted [more often / at a higher rate]. )
So most of people in Japan do not take a paid holiday. (So most people in Japan do not take [paid holidays / paid time off]. Also, if you want to stress that they don't take a single paid holiday ... So most people in Japan don't take even a single paid holiday.) 
As mentioned above, I can take a paid holiday without hesitation because not only my boss but also my coworkers in my department often take a paid holidays.