As with all things web related, for the most part you do not need to reinvent the wheel. So the first thing you are looking for is other web sites that you like.
Next, sketch out your website. Pen and Paper. Colour pencils. Crayons. Make it look the way you want it to look
Be strict with colours. Choose your palette and stick to it. For inspiration take a look at https://www.canva.com/learn/website-color-schemes/ or https://coolors.co/. In addition use contrast, particularly with text heavy sites. Black on white. Red, blue or green on white.
Keep file sizes small. Images, videos and long pages can make your website act sluggish. Files should be compressed as much as possible. Make sure you understand the basics of image file types
Jpeg is the most common, it's great for a variety of subtle colours but often results in a large file
PNG files are also large but they have the advantage of being able to handle transparent backgrounds
Next up: Writing for the web