Chat Heads Right ? Thankfully, It's pretty easy to get rid of them.

How to decapitate annoying 'Chat Heads' in Facebook Messenger.  

You never have to be interrupted by your friend's floating head again. Chat Heads were introduced several years ago on Facebook Messenger for Android. The feature uses profile pictures of the people 
you're talking to on Messenger as shortcuts for the chat—they pop up on your screen, regardless of what you're doing, and invite you to tap into the conversation. 

While the feature can be useful sometimes, it's mostly just in the way when you're doing something else on your phone. 

Messenger also has a feature that lets you directly reply from your notification bar when you need to, so the Chat Heads are frankly a bit superfluous—and again, annoying. But they're still on by default. Thankfully, it's pretty easy to get rid of them. 

Here's how :? 

In Messenger, click on your profile button on the top right. Then, Scroll down to the "Chat Heads" setting and toggle it off. You done :)