So i bought a 24" Nimbus MUni two days ago - I used to ride three years ago - now im back where i was. I can ride comfortable forward, i can turn, stop, pretty much all beginner stuff. My question is, what should i do next? I have been on road only so far, but im not confident enough for the real trails - anything i can do to prepare myself for twoish more days? Thanks 
Ride on a flowing cross-country type of mountain bike trail - nothing technical.
You will love it and will try the harder things as they present themselves. Someone else on these forums made the point that he delayed in hitting the trails because he felt he wasn’t “ready”. After he took his first ride, he wished he had done it long before.
Like a pinestraw easy to ride trail behind a school type deal? Or more of a random plot of grass riding? … Also how can i prepare for little drops and random bumps
A good idea would be to get comfortable with hopping. Then you can hop over bumps if necessary. You could also practice riding off of curbs and other small obstacles to get a feel for dropping off of things.