Everyone is obsessed with oatmeal!
You need to lower your dietary intake of saturated fat and increase your intake of healthy mono- and polyunsaturated fats. So you are looking at avocadoes, oily fish such as tuna, small helpings of unsalted raw nuts, seeds like pumpkin and sunflower. Oh yes and also keep up your fibre intake with a huge range of fruit and vegetables, a variety of grains (such as oats). Rye is good too, don't just rely on wholegrain wheat for your fibre. Watch your intake of full-fat dairy and too much red meat.
Sometimes with the healthiest diet in the world, your "bad" cholesterol may stay high, blame your parents and listen to your doctor's advice re medication etc.