1. Click on the 3 Dots on the top left, & select settings from the drop down menu.
2. Click on "Privacy and Security" then click on "Site Settings" [Some users might have to click on the "Advanced" first before seeing "Privacy and Security"]
3. Look for & navigate to "Site Settings" & click on it
4. Scroll down and look for the notification you'd like to remove and click on the little sideways Triangle and click on remove, and you are done!