Should I read manga for the slower parts?

I have just started watchin JoJo's and I am really enjoying it. I have watched till episode 7 of the first part. I have heard some parts are very slow, like part 3 or 4, but I'm not too sure about that. Which parts are generally considered slow by the community? Is it recommended that I read the manga for it if I want to get through them quicker? I haven't watched a long anime(over 50 episodes) in a few years and I'm afraid I might drop it if I get too bored and I know that later parts are really good(at least that's what I have heard), so please tell me what to do.