I decided to change my theme, before I had WP Fan Zone and I choose Stargazer theme, I was very happy with my new theme , I tested with:

https://developers.google.com/speed/pagespeed/insi...

and the speed incresed.

Also I tested with https://varvy.com/, but surprise: my Header does not have an alt text, even if I put an alt text for the Header when I uploded in Media.Very tricky, huh?

To get to the Header, go in Customize.

I tested in http://www.bing.com/webmaster/diagnostics/seo/anal..., as you see in the picture, the same result!

Using my testsite

https://my.wealthyaffiliate.com/training/using-mal...

I did it! I'll tell you how, just pay attention:

I made my header, this theme wants a header 1175px / 400px, but mine is 1175px / 100px, it seemed too wide the original one.

I chose a picture of https://pixabay.com/ I resize it using https://pixlr.com/editor/

Using Marion's training you have a good guide how to use Pixlr or Paint and resize your images:

https://my.wealthyaffiliate.com/training/resize-an...

https://my.wealthyaffiliate.com/training/wordpress...

Then I went to Canva , a good guide in using Canva is the training

https://my.wealthyaffiliate.com/training/customize...

After I did my Header I compress it using

https://tinypng.com/

VERY IMPORTANT:

Put name of your site for your header, when you save the image in your computer.

My site is called dorinasitetest, Header's name will be dorinasitetest.