How the hell works health system, how can i heal, except by use of black hearths?
So far i messed a game twice cause i wasnt able to find enought black hearts to continue in my way from village. I have just 2 or 3 of these and have no idea how or where to get more health. Heath keep going down automaticaly. Not sure if faster in daytime.

Game didnt explained this. What am i going wrong? I keep dying around area where Kain start to talk about daytime.

Sun and rain. As I remember in this game rain are make damage. Sun daytime just make you weaker. Same for wolf form. At some time you need more hits some time less sometime even more less.

Later Kain get perks to resist all of that.

Shouldn't be critical. You can drink blood from enemies and rain make very little damage.

Hearts give a way more HP if use them as medkit although automatic resurrection is easier and free up the only one slot you have for active item.

I noticed rain damage before, and Kain talked about day weakening him. But time running as fast as I have no way how to avoid this anyway.

And sure, drinking blood sounds logical, but HOW? Thats what i need to know. Or i have to find some drinking perk first?

Game turned into insane killing rush. I keep keep running forward swinging my sword on everything in my way like a psycho killer speedrunner, but its still not enough to avoid death by health loosing. In moment i start to explore crypt behind Pillars im dead for sure, no time left.
Totaly unfriendly start of game..

Game should work on 29 FPS seems like. Maybe you force it to higher somehow?
For KainGL it can be more. Still not unlimited.

Rain make very low damage, sun not make any damages (right?). As for drinking blood - it is one of the action keys. Look to controls.

For game pads you should manually bind controls. It is not native x-input game it not know about x-input game pads. Cannot be default schemes for General pads.

For FPS issue. turn off V/G/#-sync in global settings for video and display. Turn off in GOG DXCFG exe in game folder. Use fps limit option in video driver or better use third party tool - RivaTuner RTSS.
In KainGL of you play through it turn it off as well if there is such option. Use FOR limit's.

One of blood types week harmful degrees HP. But later in the game.