You can back up your messages and media to Google Drive so that if you lose your phone or switch to another Android phone, your chats are safe.
Please update the whatsapp to latest version. While updating the app you'll be greeted with a prompt to configure settings such as backup frequency, Google account, and whether or not to upload videos. After that, you can choose to manually force an upload of your chats and media, which may take a couple of hours, depending on the size of your backup and the speed of your internet connection. Here, you can also decide to allow uploads using cellular data or restrict them to when you have a WiFi connection.