My 5 month old Dutch Shepherd becomes aggressive and bites me at times, I've tried alpha rolling but that makes him more aggressive. Do you have any suggestions?

I have a 5 month old dutch shepherd. He is the second ds I have owned. He sleeps in his crate and does not get fed from the table. He is wonderful on a leash when we go for walks.

I am working with him to come when called and releasing toys with food reward. The only problem I have is there are times that he becomes aggressive and bites at me. An example is when I am watering plants and he grabs and attacks the water hose. if I take the hose from him, he bites my hand.

I was trying the alpha roll but learned quickly that made him more aggressive. I am now picking his feet off the ground and firmly telling him no. This seems to be working better. Are there any suggestions you can give me? He is otherwise, doing very well with training. There are many times that he shows submission such as lying on his back. He waits for me to go through the door first. He walks beside me on leash not in front. I will be getting him neutered when he is old enough.