You are certainly in a WhatsApp group that you do not want to leave. But at the same time, you are faced with all-out notifications that bother you all the time when you get a message from these groups. Note that you can now solve this problem by simple manipulations.
Steps

Step 1. Tap the WhatsApp icon to open the app
The app icon looks like a green bubble around a white phone handset.

Step 2. Tap the Discussions icon
If the app opens with a conversation (other than the one you were looking for), you should first press the back (<) button at the top left of the screen to see your list of private chats and of group.

Step 3. Tap a group chat
So you could open it.

Step 4. Press ⋮
You will see this button at the top right of your screen. On some versions of Android, these dots are arranged horizontally. After that, you should see a drop-down menu appear.

Step 5. Tap Mute Notifications
As you do so, you will see a drop-down menu appear with various options. When you turn off group notifications, your phone will no longer vibrate or play sounds when messages sent in the group reach you.

Step 6. Select a duration
Select the length of time you want notifications to be turned off. You have the possibility to choose between 8 hours, 1 week and 1 year.

Step 7. Uncheck the box in front of Show notifications
You will see this option at the bottom of 1 year. So when a group member sends a message to the group, no notification will appear on the home screen or even in the notification bar.

Step 8. Press OK
By doing so, you will confirm the settings and turn off notifications for the selected time interval.