How can I know if the bounty campaign that i have join is legitimate ? Really need your help guys. Thank you in advance
The only reason to know if a bounty campaign is legit is if it pays you in Bitcoin.
Seriously!
Most bounty campaigns will pay you in some ICO token no one has heard or cares about, which means that what you're getting paid with is likely worthless. You're offering advertising for free because their ICO token is likely not worth anything OR can't be traded anywhere (because no exchange covers it).
Stick to campaigns that pay you in Bitcoin and you'll know you're getting paid in a currency that can hold its value.