Hi,
I've tried to isolate the room's door according to dozens of tutorials on YouTube and it does helped to isolate the sound and deny many noise to pass by the door into the room, but noise and outside sound is still passing a little bit especially when my kids are playing and I can not wait every time till they are sleeping.
It is 12 cm wide and has 2 layers or rock-wall sheets 60x120 cm and covered with MDF 10 mm for both sides then covered by carpet all around and the same cover for the entrance for the door itself (I do not know the real name in English but I will try to explain it - that part which is between the door and the wall is covered by the carpet as well, and then I add foam between area to cover everything)
So I did goggled a lot so far and found the whisperroom.com is EXPENSIVE especially that I will ship it to EGYPT, so I've searched again and found dawbox.com manuals for building 4X4X7 V5.6 D.I.Y. Vocal Booth Plans for $55 ... but many reporting through google search that manuals are not cler enough and seller will charge again for any questions.
So I want to have a sound booth that is really isolate the sound especially that I am recording in my bed room and next door my crazy kids, so now I've the door isolated to some extend.
So what shall I do?
Thanks

I'm afraid just using carpet or MDF, without understanding all the construction details, is just silly. Every detail is very important: walls, floors, ceiling, doors, acoustic isolation, vibration isolation, framing, skins, hardware, caulking. It's not possible to explain all the details here. You could devote a chapter or more to each one of those items I've mentioned. You will really need good drawings, charts, and a lot of text, to understand the subject well.

Would you go on an forum of car owners, and ask them how to BUILD your own car? No. OK, then the same situation applies here.

If you are really serious about this, you should hire a local architect to design it for you. Then look at the plans and decide whether you want to try to build it yourself, or to hire a contractor. Otherwise, buy a book written for architects, that talks about acoustical treatment. There are college textbooks that cover this topic. Start at a university library. That will at least give you some idea of the complexity involved.

I remember lengthy discussions here, with you, about the simplest audio topics. Many people tried to help, but in the end there was still a lot of confusion. I think the subject of acoustical construction is even more complicated than some of those simple audio topics in the past. I, for one, am not even going to start down that path with you. Really, you need to consult a local expert.

With two layers of plasterboard and MDF, the mass content is pretty high - so it's more likely your room is leaking somewhere? A simple test is a microphone connected to some sealed headphones. Shut yourself inside, and arrange something noisy outside that you can hear with your ears, then go around the room with the microphone and try to find a leak. Best guess is always the doors - the door may well close but not seal - especially at the bottom, and the other likely place is the join between the wall and ceiling, and wall and floor.

In practical terms, most problems come from gaps you can't see, that allow sound to pass unimpeded, rather than going through all those layers. With a mic/headphones, leaks are simple to find.