I downloaded the “WeMod-Setup.exe” and started it, it downloaded the necessary data, but then, the “WeMod-Setup-637518452234270940.exe” is sent in the quarantine zone of my Avast. once I get it out of there and start it, it just say “installation has failed ; fail to extract installer”. please help.
Welcome to the community. 
However, please use the search button before posting, as this has already been resolved many times.
Follow the instructions in this post: I can’t Install WeMod / "There was a error installing the application" - #2 by Ravenfyre.
If the problem continues after doing so:
- Restart your PC.
- Open your antivirus and go to the quarantine/virus chest menu.
- Whitelist and de-quarantine any WeMod files from here.
thank you for your time and quick and well explained help!