How to fix offset direction?

Hello, guys. I am new in Grasshopper and I am still learning. I have 2 problems which are probably very easy to be solved from you, so I hope you can help me.

Problem 1: I've created 4 different closed curves as starting areas for making them surfaces and extruding them but only one of them is going positive in the Z direction, all the others and every other that I create are going negative and the surface is with darker red color as you can see from the attached file. How can I fix that and make them go positive in the z direction?

Problem 2: As you can see from the attached file the plane is positioned in the middle between all the curves which effects the scaling and the rotation of the extruded components and they don't change around the surface but are going on a side. How can I put plane under each curve and manipulate the curve around this plane?

Thank you in advance!