Let me know how you are getting on. How are you getting on in your new job? If someone says the sentence above, it´s why he or she wants to know about your progress in your new job. --- How have you been? ( Present perfect ) It´s similar to "how are you?" - The interlocutor wants to know about you, about your life, a new job, a new activity or about what you have done lately. PS: English is not my first language, but I hope it helps.