please, let me see complete sentence. i don't know what do you mean. so I don't think you are a fool. 나는 네가 바보라고 생각하지 않아. i don't think you saw that. 나는 네가 그것을 봤다고 생각하지 않아.

A: "I'm nice." = 나는 착해. (naneun chaghae.) B: "I don't think so." = 그렇게 생각하지 않아요. (geureohge saenggag haji anayo.) B: "No, I don't think you're nice." = 아니요. 나는 너가 착하지 않은 것 같아. (aniyo. naneun neoga chaghaji anheun geot gata.) For other examples just change "chaghada" with other verbs! Hope this helps!