I've been following r/cscareerquestions for two years now. It is one of the best Computer Science career-related subreddit. You will get all types of help related to your career in the tech industry. Recently there was a post for a collection of free resources for CS folks.
In case you don't use Reddit or didn't see the post, here is the link for the same, please have a look. It includes resources for interview preparation, system design, behavioral questions, books, courses, etc.