W3C validator errors

Hi! I just run my site(sample ignore the about us section since it’s undergoing some restructuring)- https://kafolabi.github.io on the w3c validator. It’s also showing me a list of errors. Pls can someone experienced explain the errors to me and how they can be solved? I heard it improves SEO a little. Thanks and happy coding!
Here’s d URL of the validator

For the link errors you should copy the entire message and paste it into Google and read up on why the error appears. That will provide more info than I can type in here.

The style appearing between head and body message is because you have elements incorrectly placed. You can review this for an understanding of the HTML boilerplate tags.