National Holidays

There are many national holidays in Indonesia: as many as in Japan.

I'm not sure that most Indonesian people can take a day off on national holidays.

I suppose that most Japanese people work on national holidays, except for those who work at a famous company.

Most of the stores in Japan are usually open on holidays so that you can receive many services during your stay.

But public institutions like hospitals police stations, city offices, and what not are not open on holidays

There are as many national holidays in Indonesia as there are in Japan.

Not sure if this is what you are trying to say.

I'm not sure that most Indonesian people can take day off on national holidays.

I suppose that most Japanese people work on national holidays unless they who work at famous company.

You already stated the subject with "most Japanese people" so you just need to refer to the subject using they.

There are many services available when you stay in Japan, many stores in Japan are open on holidays too.

However, public services i.e. (hospitals, police offices, city offices, etc.) aren't open on holidays.

I'm not sure that most Indonesian people can take the day off on national holidays.

Most of the stores in Japan are usually open on holidays, so that you can always go to them when you stay in Japan.

But public services, like hospitals, police stations, and city offices, aren't available on holidays.

Usually the phrase "and what not" is only used when speaking, not writing. In writing, 'etc.' is more acceptable.