Text with custom font and overlay on grey background

hola, how do i insert a custom font style with a grey background, like on my screenshot? If i use the squarespace "text-tool" i just can chose the headline-presets, and if i pick one, the whole row changes into that headline font. So im not even able to realize the text design like its on my screenshot, then i'd like to have a grey background for each textbox, preferably a overlaying effect like on the screenshot. How do i realize this? Is there a right code, that i can put in the "squarespace code box" for my specific site? Im so sorry, but coding is my weakness, im hoping someone can help me!

Live page: denniseming.de/vita
(this is my current site and i used svg images to realize the look, but its not the best and cleanest way and the font size is different to the other sites, its not a good corporate design :()

Thank you very much!!