"过往"means：1、something happened in the past which impressed you our someone. As an adjective or noun eg:过往的悲伤（sadness） （as an adjective）or 回忆过往（as a noun） 2、come and go. People or cars go through,passing. eg:路上过往的车辆很多（There are a lot of cars passing on the road. ） 3、 have friendly intercourse with. eg:我和我的朋友过往很密 "来往"and“往来”1、have almost the same meanning, I think "get in touch with" maybe better. eg:我与他之间来往（往来）不多（I don't get in touch with him very often.） 2、The same meanning as the second point of "过往" “交往” 1、get in touch with