Is there any resources that I can use to learn about the fundamentals of LoR (or card games in general)

I've been playing for a few months now and I absolutely love the game. I watch as much high level gameplay on Twitch to learn and improve, but sometimes I feel like I don't understand why good players make some of their decisions. For example, sometimes Swim will be incredibly sure of a play being the correct one and it's completely different to what I would do. On top of this, I feel like sometimes I'll make a decision and then notice a silly mistake right after. Thanks for reading and I appreciate any help that is posted!