LOL~
As matzik said, everything is about time, I suppose. The more you read and the more you like the series, the easier it goes for you to remember the names. Several manhwa used quite almost like Western names or popular names you hear from Korean artists or something so it might be less hard, but for others, you just have to remember it step by step. No rush and enjoy the story, you'll get there eventually. It took me so many chapters in Tower of God to remember the characters' name properly, just so you know, and I think by now I have forgotten most of them again. XDDD