re-entry permission

Hi users!!
i heard that i dont need anymore a re-entry permission ,that is true??
and how many days i can stay in my Country and back again in Japan?i can just fly without any worries or i have to inform the shyakushyou??

I don't know your visa status, so I'm going to assume you have a work visa (like Specialist in Humanities and such).
If that's the case, you don't need to apply at Immigration for a Reentry Permit. You can just go to the airport and fill out a small form they have available there (after security, where you pass immigration control) called a Special Reentry Permit. It's a small and simple slip of paper they staple to your passport.
With that, you can be outside of Japan for up to a year. If you fail to come back within a year, your residence will be canceled.

http://japaninfoswap.com/embarkation-and-disembarkation-card-card-chan...

Read this and also it show sample how to fill the card properly.
Make sure yot tick the correct box.
Special re-entry aplicable if you plan to re-enter Japan within 1 year.
Anything more than 1 year you need to apply for the re-entry permit at immigration office.

ok!
and if i want to leave japan before my visa expire??i have just to leav it or i need to communicate to the immigration office??i am sorry to write that but i dont feel so comfortable here in Japan with all this overwors hour.

In that case, just make sure you tell the shiyakusho/kuyakusho that you are leaving.
Then, at the airport, when going through immigration, do not fill out the Special Reentry Permit and tell the guy at the booth that you are leaving for good. He will punch a hole in your residence card and your residence status will end.