Most of people who got scammed lost their BTC on shady exchanges, how's OS relevant in this case?
after I use Windows, I have been robbed and now I switched to Android, whether the risk will be higher?
Why not buy a hardware wallet ?
where can I get it? I do not know about the hardware wallet
Hardware wallets like Trezor are effective in stopping malware since there are currently no designed for it and they have anti keylogger features. IMO it is a good investment for huge amount of BTC. For small amounts go for paper wallets generated on offline computer.