My dad

I'm 16 and currently a junior in high school. 3 years ago on my birthday my dad was diagnosed with Alzheimer's. As time started to move on from that. I could see changes. Now three years later he is progressing faster and anger is coming with it. He gets angry over everything including small things. I don't really know what to do anymore. It's getting stressful. Any suggestions or help would be really great.