Where does North Korea find scientists to develop its missiles in order to continue the development of their scientific research?
Do they have any education background or they hire foreign scientists? If they hire, from where and how?
They were likely trained in Univeristy as North Korea does have Universities that cover the topics needed to educate scientists enough to pursue further research on missile development. I regret that I could not find any concrete articles specificity on this however I found some evidence that leads to my conclusion.
North Korea education in general: (reference)
Children go through one year of kindergarten, four years of primary education, six years of secondary education, and then on to universities.
North Korea University: (reference)
Kim Il-Sung University's colleges and faculties include economics, history, philosophy, law, foreign languages and literature, geography, physics, mathematics, chemistry, nuclear power, biology, and computer science.
Not on topic but related:
If you are unsure of how nuclear science made its way to North Korea, the former Soviet Union helped North Korea develop a nuclear power program. (reference)
Most North Korean military technologies are the remnants of the Soviet Russian and Chinese technologies.
They usually modify them but don't actually develope a whole new type of anything.
I am not totally sure but those technologies are free to use or modify because they were either given to North Korea for free or they were free to use due to Soviet or Communistic Chinese ownership( which I think means no patent).
North Korea seems like it has a lot of fancy military gears but as far as I know those are quite old and a few generations behind.
There is some indication that Russia has been partnering in training them for years: UPI
Moscow may have allowed several North Korean nuclear researchers to work at Russian nuclear sites, including a scientist who is under United Nations Security Council sanctions.
The North Korean nuclear scientists were allowed to engage in their research in Russia until early 2015 when Pyongyang stopped paying an annual membership fee to the Russian government, Japanese news agency Jiji Press reported Monday.
North Korea buys its missiles from Russia and China. They get modified by the scientists. They learn by doing. If you do something often, you'll understand it better. There are universities that teach nuclear development.
China highly supports North Korea. Russia just sells weapons to every country. Including ISIS (which is not a country).
North Korea is scary. They have hydrogen bombs. We should look out.