I couldn't help but notice that many players complain when crossfire is played on the server. I think this happens due to the fact that it is indeed an incredibly difficult map especially for smgs since their purpose is to mainly rush. This is a video from a player called phantasy with many tips and things to do on promod. He was a really good player. I hope that this video will help you get better. If the feedback is good,I will take time to post more topics on different maps, tactics etc for you.