Watching your latest Witcher videos:
Right off the bat: You need to treat each individual video as it's own entity. Start every video with an introduction of who you are and what's going on. If it's a multiple part series, talk about what happened last time, and discuss what you are planning on doing with the current video. Make it so any viewer can jump in on any video and not feel lost.
As for the running times, most of your videos are 20+ minutes. Cut down on that time. People are much more encouraged to watch a 10-15 minute video to completion than 20+ minute one.
Watching some of your videos, I see you playing video games, but I don't understand who you are. What separates you personally from other video game YouTubers? That's what you need to focus on.