Try holding down on a notification (long press) and then you can go to the "App Info". From there you can see what app is causing these ads and get rid of it.
You have a free app installed that is doing this. You have to try and figure out what app is doing that and remove it if you want or see if there is a paid ad free version.
You can also install an adblocker such as Adguard that will prevent this from happening. For me, this is the best way to go.