Text formatting issues on Coming Soon page

I’m finding it impossible to get the text to look ok on my coming soon page, which I have to keep disabling. I don’t seem able to change the font to one I want, the font size isn’t right, and the paragraph breaks keep going out. I also keep getting large grey or black rectangles appearing over the text, as though the heading and a space above it is highlighted. I can send screenshots privately if it will help.

Many thanks in advance for your advice.
Lindsey