How do i prevent damp?

You need drains outside to divert the water at base of slope. You don't indicate where you are located, but some plantings will absorb much more water than others. Contact your county agricultural extension agent for more detailed advice. Water beneath windows is indicative of missing or loose caulk, or flashing needing replacement. Try running air conditioning and a dehumidifier set to 40%, with its hose going outside a window or into a floor drain.

well, great! now you can get it remedied to protect your property -- may take more than you can DIY, grading, etc., to slope the ground away from the foundation. Any plantings around the foundation should be kept to the outside of the roof line ... so that water off the roof will drain away. You can put 'mulch' behind the plantings to help retard weed growth, but leave at least 12" of bare soil directly next to the foundation itself.