The chat built into the Gmail website was handy a few years ago when Hangouts was still used moderately, but since Google turned its back on Google Allo, all it does is take up space: this disables the chat from Gmail.
The Chat of Gmail, based on Hangouts and previously in Google Talk, occupies a privileged place in the sidebar of the Gmail website, disputing the little free space with the labels. If you do not use the chat and you want more space for the tags, disable the chat entirely.
If you want to eliminate Gmail chat ultimately, you must go to the Gmail settings. On the Gmail website, click on the options icon and then click on the Settings menu in the drop-down menu.
The Gmail options page may be a little intimidating because it has a lot of options and subcategories. Luckily, we do not need to dive too much to find what we are looking for. Click on the Chat tab.
Here you must check Chat Off and then click on Save changes so that the chat in Gmail is entirely disabled. If you have Hangouts installed on your mobile, you will still be connected, and you will continue to receive messages in this way. If not, you can always open the Hangouts web page to chat and start video calls from there, instead of Gmail.
You can also make it smaller
Does Gmail chat bother you but not so much that you want to erase it completely? In this case, you can make it smaller by clicking on your name and then check the option Use dense roster.
This removes the photo from the contacts, making the listing more compact so that they fit more per screen. If it still bothers you, you also have the option to click on the chat icon to minimize the chat. If you click on it again, it reopens. Gmail will remember this the next time you open it.