How to change Header, navigation bar, text box font to Synonym and Roboto Mono on home page and whole site?

Hi all,

-Homepage

Could someone possibly help me change

1. Navigation font (Home, Work, About) to Roboto Mono?

2. Header (Hi I am Kacy, UX UI .....commitment) to Roboto Mono?

3. Text box:

LanguageLand and Academic Project / UX Designer to Roboto Mono?

Body (A mobile-first....pals function) to Synonym?

-Work page:

I am also looking into changing the font for a whole case study page here: https://www.kacy-jung.com/case-study-1-languageland-1

Is there any way that I can flexibly change the font to Roboto mono and Synonym wherever I want?

Thank you so much for the help and I really appreciate it!

Question 1. Navigation Font

You can do this easily in Site Styles

#1. First, click on the Site Styles icon

#2. Next, choose FONTS

#3. Click on the blank space in the Navigation bar

The fonts I want to use aren't in their options!