Learning shaders

Advise materials literature or tutorials on writing shaders according to this language HLSL and is it sufficient to know only that language to write high-quality Shader?
What me need to know to properly and efficiently make a Shader?
Sorry maybe for stupid questions, I ask because writing a Shader I’m a complete goof. And I very much want to learn, and to start with the right things in learning shaders!
Thank you for any information!