Hello, right now I am using piskelapp.com to make my sprites and background images. I like pixel art but I would like to learn to draw hd graphics. Are there any better desktop programs/website that are better?
There are many apps, depending on what you need and how you like to work. There's the stock Adobe stuff, Photoshop and Illustrator. There's Pixelmator and Sketch on Mac.
Sketch and Illustrator are focused on vector artwork, which scales very well for HD and 4K+ displays. But it depends on what you want exactly.
Gimp is free to play with. Lots of tutorials.
I use "Graphic" a cheap illustrator type program.