Struggling with Routes & Networks in LRDI – Need Free Resource Recommendations

I’m currently preparing for CAT and finding LRDI quite challenging, especially the topics related to routes and networks. I often get stuck in understanding how to approach these sets and end up taking too much time or not solving them at all.
I’ve covered the basics, but I feel like I’m missing the right approach and sufficient practice for this specific type. Can someone suggest good free resources (YouTube channels, playlists, or websites) that explain these concepts clearly and provide quality practice?
Also, if you have any tips or frameworks to approach these sets efficiently, that would really help.