Sok sabay Ravy. Do you understand the basic tenses of English (past, present, future?) Perfect tenses are a bit confusing, so if you'd let me know I could assist you with your English. I'm trying to work on my Khmer as well.

I'm not sure if you could understand a full explanation, so try this link for a start: http://www.ego4u.com/en/cram-up/grammar/present-perfect-simple