Characters don’t exist in a vacuum. You must describe them, the world they live, and the atmosphere that surrounds them. So, how much description do you need to put in your book? The short answer is enough to make your readers feel a part of the story, but not so much that it causes them to stop reading, roll their eyes, and skip to the next section of dialogue.
Today, pictures are everywhere. Most readers will already have an image of what you are trying to describe. They have imaginations. You don’t need to go into excessive detail unless it is an important element of the story. Even then, be careful. I once read a novel which used a lengthy paragraph to describe a tiger, an essential character of the book. Every single hair was mentioned. I like tigers, but I got bored in the middle of it.
Don’t get carried away with your descriptions. Just make sure you include enough to anchor your readers in your story’s world.