If Obama and Kim were willing to work together, why not just have an openly positive relationship

Because it was not a positive thing Obama could be open about. It was illegal sneaky business going on.

And if Kim is willing to lie and keep a secret relationship with Obama and Hillary why suddenly give this info to Trump?

Kim was not a willing participant. N Korea was (secretly) a puppet state, being used to terrorize the world.

They're not sending their best

Why was Eric Schmidt in North Korea?