Suffering is pain. The purpose of suffering is to realize it as much as one realizes pleasure. Suffering is a lesson of this life, once this lesson is learned suffering ceases to exist.
Suffering is a signal you are doing something WRONG or in the WRONG situation at the WRONG time in the WRONG place. It's the smack in your face to do a turnabout or at least ponder what you may be doing WRONG!
Some suffering is caused by the WRONG of others like assholes who run you over with a semitruck, for example. Suffering is inevitable.