So what OS must we use ?
(To be honnest I'm looking for to change my PC and I'm currently looking for more safety)
You may have heard already that there are less viruses made for desktop Linux (server Linux is a different story) than Windows, so Ubuntu LTS isn't a bad place to start. Vendors are starting to make versions of their programs specifically for it.
Alternatively, Linux Mint is based on Ubuntu and has mostly the same UI as Windows.
However, I think common sense is the best way to not get hack.
Yeah. If you see App A that has 500K downloads and an app B that pretends to look like App A but only has 5K downloads, then you have a pretty good feeling that App A is the real app and App B is a "fake" copy.
It's harder for fake apps to get hundreds of thousands of downloads, because the services they pay for to inflate downloads only have so many accounts and devices.