"safe" is just some slang meaning like "cool" "laters" would just be a short way of saying "see you later" - but it sounds really a bit lame and try-hard to me

"safe" is just some slang meaning like "cool" "laters" would just be a short way of saying "see you later" - but it sounds really a bit lame and try-hard to me, or the kind of thing a middle-aged, middle-class person would write as dialogue for a working class urban teenage character in a TV show. I think quickthrower2 is saying the same thing but maybe they can correct me (sounds like they're England, so they'll know better than me). Don't worry about either, you won't hear them particularly often :)