This was I what I wanted to say yesterday.
The dynasty adopted it as a religion to rule the people.
The next dynasty adopted Confucianism as a religion to rule the people from 1400 D.C. to 1900 D.C.
There is no more king in Korea, but the tradition of the two religions is still in our culture; seeking for peace and respecting seniors.
People in Korea believed in Buddhism from 800 D.C to 1400 D.C.
The dynasty adopted it as a religion to rule the people.
The next dynasty adopted Confucianism as a religion to rule the people from 1400 D.C. to 1900 D.C.
There is no more king in Korea, but the traditions of the two religions are still embedded in our culture; seeking for peace and respecting seniors.
I love this, thank you so much for writing it! I so appreciate learning about your culture, it is truly fascinating and you are definitely giving me a major sense of wanderlust to come visit 
Your writing is very strong. I only made some minor edits. The names of religions are capitilized so I adjusted that. I also made "tradition" into "traditions" because you listed two types of values in the culture. The addition of the word embedded was just for extra clarity, but the sentence you wrote was still totally grammatically correct. Awesome job.