Verb: mess with
Meaning: Become involved in something damaging or dangerous
He’s been MESSING WITH cocaine.
Meaning: Annoy, bother
Don’t MESS WITH me or there will be trouble.
Meaning: Associate (negative)
He’s been MESSING WITH some dangerous people.
Meaning: Try to repair or improve, usually unsuccessfully
She’s been MESSING WITH it for hours and it still doesn’t work.