how to temporarily disable free avast firewall

So, for example, if i'm installing software (like Skype, which downloads Setup Files directly from internet) or updating software via built-in updater, it is safe to install/update software when antivirus protection is temporarily disabled (I mean, can any malware enter into my PC from internet in this way, during software installation/update process)? Or it is just a myth. I heard that prior any software installation it is recommended to disable all running programs running in the background (including Antivirus), in order to install programs, games, and drivers successfully, without mistakes. Thanks in advance (and sorry for my poor English). And a second question: can I run Avast Antivirus together with Windows Defender at the same time? I always run them both, but friend said that I need to turn off Windows Defender, because there can be issues running them both.

? I noticed that many programs, games recommends temporarily to turn off antivirus protection during the installation process (in documentations).

I'm new here, and I have few questions about security:

How to temporarily disable free avast firewall