Christians: Do you really go to hell if you're not kind to people and do good works?

You understanding is correct, salvation is based on faith in Jesus, not on works (Eph 2:8-9). However there is also the flip side to that being that if after you put your faith in Jesus, if you life does not change, there are no 'works' to speak of, did you actually put your faith in Jesus. But in this case it is rather that works are an evidence of faith, but not a means of salvation. Heaven and Hell are about sin, are your sins forgiven by Jesus or not? Doesn't matter how 'moral' you are if you don't have forgiveness of sins.