@Kusanar you can build swales on your slopes to catch rain run off and retain the rain for your pastures. We are on a slope too, The front of our property to the house drops 10 feet, then goes to a gulley that cuts behind the horse barn, and drops even further. We had to haul in dirt to level up the horse barn. We have several swales on our property that was built in the 1930's by the CCC, Civilian Conservation Corps. There are swales all around here, built by the CCC. plus they planted trees and improved the lands. Anyway, swales do a lot to help the land. We have made swales behind the horse barn with wood chips that were the result of having clearing done by a forestry mulcher. I sowed grass seed in early spring and have a decent stand now. I am letting one horse graze it a few hours a day for now.
It looks like you have good grass on your land, you can improve it by sowing clover. Clover will fix nitrogen in the root nodules, making it available to the other grasses. If you graze the sheep on clovers, provide baking soda free choice to keep them from bloating and limit their grazing at first to give them time to adjust to it. I also provide dolomite lime to my sheep, the magnesium in it helps to prevent grass tetany.