Is it okay to go back to country?

I am a long term resident (single entry) in japan for just a months and they give me 1 year to stay in japan and I have also a residence card and it will be expired in 2018 December 02. Can I go back to my country where I grew for 6 months? I still need to get special re entry permit? And it is okay after 6 months when I go back in November line of 20 that�fs the time I will renew it is okay? And it will not be matter in my passport that it is single entry?

No one here can answer this question with accuracy. You need to talk with someone in your regional immigration office. Look up the phone number and call. Or if your Japanese isn't up to snuff, have someone call for you. Or if you are close enough to go in person, take your documents and go to the office. Good luck.

Yes, you can exit and enter Japan within one year or before your status expire Dec.02, as long as you tick/use the special re-entry permit on the embarkation card.
http://www.immi-moj.go.jp/newimmiact_1/en/point_3-4.html

However due note that being away long time may effect your status renewal.

Single entry in your passport is only for your Visa. It mean you can only use that long term visa to enter Japan once. So you used it one time to enter Japan and was given long term resident status i.e. zairyu/resident card.
So that single entry visa on your passport is no more valid.

You need visa to enter Japan and once entered with visa you are given resident status. With resident status you can leave and enter Japan within one year or status expire, using the special re-entry permit on the embarkation card at airport.

For longer stay out more than one year, you need to apply for re-entry permit at immigration office.

"Fact-check" is paramount for your case, the responsibility is entirely yours.
As Kotae said " contact regional immigration office" to confirm.