How to archive conversations on Facebook Messenger and see your archived messages

You can archive a conversation on Facebook Messenger using the website or mobile app, and then see those archived chats later in another inbox.

How to delete individual Facebook messages or entire conversations on your computer or mobile device

You can delete Facebook messages using the Facebook Messenger smartphone app, or the Facebook website.
ZDNet

You can delete sent text messages on Android now - here's how

Google Messages now lets you delete a sent text message. A deleted message disappears for the other person immediately. The feature is available now for almost all Android users. Get more in-depth ...