If a favour from a stranger sounds too good to be true, you should suspect it to be a Greek gift. All you've to do when faced with such a scenario is to look for the loophole. There's always a loophole. Find it. It's hard to find strangers who run charities in cryptos. There must be something they ask for in return, sometimes it's hidden.

When next you find yourself in such a situation and you feel you don't want to let go of that opportunity (because actually that point was where you should've left the group), create a fresh wallet and deposit a minimal amount to test run it. Don't ever use your main wallet with huge funds in it.

Sorry for your loss, anyway. It's the cost you pay for experience. Most of us here have gone through one form of such loss or the other. That's what makes us advise newbies of certain things to avoid from the point of experience.