Most cloud mining sites are scams, but scam or not, cloud mining is almost always a losing investment.
Regarding hashflare.io: even if it looks legitimate, it is still a money-loser.
For each 10 GH/s Bitcoin contract you buy, you will pay $1.20 plus $1.44 per year in maintenance fees. After one year 10 GH/s might mine 0.002 BTC, currently worth about $2.00. You might break even after two years, but it is more likely that you will never break even.
Yeah. It may be safe to join the site, especially if you have anti virus and use it from your home wi-fi, but cloud mining surly will not bring you that profit you are expecting for, the same way you may join to a faucet. Good luck!