New player here.
Do I need to play the Chapter 1 and 2 first to understand the story continuity or each chapter is designed as standalone story?
As has been said they're disconnected. Same world, same mythology, different settings, different characters, different stories. I recommend at least playing HC2, as HC1 is fairly limited by comparison and relies a touch too heavily on certain NTR tropes that I don't like such as
The one warning I will give is that the NTR is unavoidable, it is an intrinsic part of the story and there is absolutely nothing you can do to stop it from happening. At the end of the game the female characters will have been used and abused repeatedly and at certain points in the story begin to prioritize their pleasure over anything else. HC2 in particular goes out of its way to emasculate the main character, he is shat on just about as often as the game will allow. So if you're the kind of player who puts yourself into the role of the main character... do not play the HC games. If you're the kind of player who wants to do the cucking instead of being cucked... don't play it. I feel like I need to reiterate that first one... the MCs of the HC series are largely silent protagonists... if you have a tendency to imagine yourself as that character then don't play it. The hero is the main victim here. Beware, abandon all hope ye who enter here without an interest in corruption and netorare.