The black streaks that appear primarily on the roof edges and under the windows of your vehicle are known as so-called rain streaks. These rain streaks occur because rainwater mixes with vehicle dirt and sealant and then runs down the vehicle. This is not a concern and is completely normal.
With the right cleaning products, which you can obtain from your Carado trading partner, it is possible to remove the rain strips quickly and easily without damaging the adhesive. Talk to your dealer and pay attention to the compatibility with the vehicle when selecting the cleaner.