Android Whatsapp constantly notifying about web login
Android does give you the ability to configure the notifications you receive, 

There is a nice guide on the whatsApp FAQ section of their website https://faq.whatsapp.com/en/android/26000003/.

Summary:
There are 2 areas that you can alter notification settings
1. Navigate to your phone's Settings app > Apps &amp; notifications > WhatsApp > App notifications. Adjust settings here to your desired requirements.


Open WhatsApp > tap More options  > Settings > Notifications. Here you can set notifications for messages, groups, and calls