You can edit very easy.
While on the page, press the F12 key on the keyboard.
Click this icon at the top left of the console.
Then select the area you will edit.
Try changing the codes on the right.
Once it’s the way you want it, copy the codes.
Admin > Customize > themes and click EDIT CSS HTML
> Desktop
Paste and Save.
You can instantly see what you saved on the site.
You can find the codes you are looking for on the internet. For example, if you want to change the background color, search on Google for “Background change code CSS”.
The codes you will find are “background-color: #fff”
You can give the background color you want by adding the code you found to the edited field.
Since your native language is English, you can find resources much more easily.
I edited the site in my profile without any coding knowledge. You can do it too.
Good luck.