I DON'T KNOW WHAT TO DO!

I have a 5-month old beagle puppy. We had him since he was 1-month old. I haven't been training him much, I want to start training him actively since I can't make him listen to me. He guards his food and he becomes aggressive when we come too close. I am afraid he will grow up to be a bad dog so I want to actively train my dog now. I work in the night shift and I don't know what to do.

I don't know where to start. What to teach first and what to teach next. I've been watching multiple training guides on youtube but I feel I am not getting the information I need. I am currently looking for a trainer but I want to train my pup myself. He poops and pees in his crate as well. I really don't know where to start at this point. Please direct me to any forum link or thread that might help me please.