it'a pleasure:- Thanks for your help.- It's a pleasure (没有关系)
it' my pleasure A: Thank you for your advice.B: it' my pleasure/It's a pleasure (没有关系)
a pleasure------- It is a pleasure to talk with you ----和你交谈是种乐趣
my pleasure： - Thanks. -My pleasure / it' my pleasure/It's a pleasure (没有关系)
with pleasure -----很乐意,很情愿--------Can you do it for me ? -With pleasure.
with my pleasure (英语中应该没有这种表达)