Only do this when you're preparing to install another piece of software, as doing so will entirely stop your antivirus protection. Here's how to turn off avast antivirus fully without needing to uninstall it.

All shields are disabled at the same moment.
Step 1: Right-click on the orange Avast sign on the Windows taskbar to enter the antivirus Avast's settings.
Step 2: Go to Avast Shields and disable one of the options, such as temporarily disabling the shields for 10 minutes, an hour, or until the computer is restarted, or permanently disabling the shields.
Step 3: After clicking "OK" to confirm the specified option, all shields will be paused for the amount of time you specify.