1. Wait a Little Longer: Sometimes installations can take longer than expected, especially if there are updates or if your system is busy. However, 20 minutes is generally too long. 2. Check for Activity: Look at your system's task manager (or activity monitor) to see if the Firefox installer is still running or if it's consuming resources. If it's not responding, it may be stuck. 3. Cancel the Installation: If it appears to be frozen, you can cancel the installation. You may need to force quit the installer.

   4. Re-download Firefox: After canceling, go to the official Firefox website and download the installer again. Make sure to download the version that is compatible with your operating system.
   5. Run as Administrator: If you're on Windows, try running the installer as an administrator by right-clicking the installer and selecting "Run as administrator."

6. Check for System Updates: Ensure your operating system is up to date, as sometimes pending updates can interfere with installations. 7. Disable Antivirus/Firewall Temporarily: Occasionally, security software can block installations. You might want to temporarily disable it while installing Firefox, but remember to enable it afterward.

I downloaded new version and it says it is "Now Installing installing" for last 20 minutes. Should I try to re-download and try again or let it wait?

Try the full offline setup from https://www.mozilla.org/firefox/all/desktop-release/ if you are using the small online stub installer.