Not sure the following actually works but it might...
You can go to User Control Panel from your login name at the top-right. Under Managed subscriptions, it shows what forums you are subscribed to.
Under Board preferences, Edit notification options, you can select Email for “Someone creates a topic in a forum to which you are subscribed” and “Someone replies to a topic to which you are subscribed.” However, I don’t think you automatically get subscribed to a topic just because you are subscribed to a forum. You could do that manually once you receive notification of a new topic, if interested.
You can subscribe to each forum of interest by going to each forum category then each sub-forum within it and at the bottom-left of each sub-forum, click “Subscribe.”