Press the “ESC” button on the keyboard or click on the computer icon from the icon bar at the bottom left of your screen in-game, to open the “Settings” window.
Click on the “Interface” tab and then click on “Mouse” in the list. From here, you can adjust the “Look Speed” slider to your preference.
The slider bar can be moved from 1 to 10. The higher the bar is set, the faster your screen will turn when you use your mouse.