Oda

Can you share link to your site? We can check button code easier
Or try this code first
.sqs-cookie-banner-v2-cta * { font-size: 12px; font-family: 'DMSans' !important; }  

You can adjust 50%

I tried by myself, but my headings still look the same on my iPhone, sadly.
 
@font-face { font-family: 'EksellDisplay'; src: url('https://static1.squarespace.com/static/61d56b82725cde14d95764f9/t/61d56d158491b024edd96292/1641377045670/EksellDisplayLarge.woff2'); } h1 {font-family: 'EksellDisplay'; letter-spacing: .0em !important;} @font-face { font-family: 'Apercu'; src: url('https://static1.squarespace.com/static/61d56b82725cde14d95764f9/t/61d56cdc4404080eb812179f/1641376988511/apercu-bold-webfont.woff'); } h2 {font-family: 'Apercu'; letter-spacing: .0em !important;} h3 {font-family: 'Apercu'; letter-spacing: .0em !important;} h4 {font-family: 'Apercu'; letter-spacing: .0em !important;}

Nevermind! I solved it by inserting !important 🙂
#site-title {font-family: 'EksellDisplay'!important; src:local, url(https://static1.squarespace.com/static/61d56b82725cde14d95764f9/t/61d56d158491b024edd96292/1641377045670/EksellDisplayLarge.woff2)}