Hello and welcome to the forum. Yes, physical activity has been shown to help lower total cholesterol. It does this by increasing HDL cholesterol which then counters the bad cholesterol, LDL, which improves your total cholesterol number. Physical activity will also help you lose or maintain appropriate weight which is important as well for cholesterol. https://www.webmd.com/cholesterol-management/features/exercise-to-lower-cholesterol#1
As to how often, this has been debated. But the American Heart Association recommends 30 minutes per day of moderate to vigorous activity such as walking, biking, swimming a day. And that is for at least 5 days a week. And remember, all exercise does count, even gardening and house cleaning.
Best of health to you.