Hello, Hoco!
For the first post, …it’s not possible with the standard blog page.
You can create a new page, and set up a blog on that page with the Visual Composer.
In that case, you can have a header.
Maybe post below can help you:
https://theme-vision.com/forums/topic/edit-blog-page/#post-5663
For the second post,
Add the code below to the :Customizing->General->Additional CSS
code:
#toTop {
display:block!important;
}
https://prnt.sc/gqc96s
Regards