Google would be very happy if you used its Chat application, so pleased that it's pushing it beyond the boundaries of its actual app. Last month the tool became available to regular users (who don't pay for access to Google Workspace), and now its integration with Gmail is available to them, too. But it isn't turned on by default, so if you'd like to use it, you have to go digging in the settings menu.
First, open the side menu in Gmail, scroll all the way down to the bottom, and tap "Settings." Tap your personal Gmail account on the next page.
Scroll down to the "General" area of the list. The first option should be "Chat (Early Access)". Tap it. On the pop-up alert, tap "Try it."
Gmail will reboot, which can be a little jarring. Open it again if it doesn't pop up automatically, and you'll be greeted with a new bar on the bottom of the interface. "Mail" is your standard mailbox, "Chat" takes you to the official Google Chat application with all your text conversations, and "Rooms" is the ongoing conversation view. (Like Slack, but basically useless.) You can switch between the three views at any time.
If you want to remove Chat and the bottom navigation bar entirely, and you may indeed want to, just follow the steps above again.