How to I Change Gallery Headings and Header 'Contact Us' button to Custum Font

Site URL: https://carillon-goby-8nw8.squarespace.com/gallery

This is what I have been using. Feel like I have tried everything to change these but nothing seems to work!

@font-face {   
font-family: 'HV Simplicite';   
src: url('https://static1.squarespace.com/static/60055609dfad4a36491fe02a/t/60055ab58a2b87460a1cf12b/1610963637776/HV+Simplicite+Italic.ttf'), url('https://static1.squarespace.com/static/60055609dfad4a36491fe02a/t/60055a49dc5a6f13a1836ca9/1610963529783/HV+Simplicite+Regular.woff'), url('https://static1.squarespace.com/static/60055609dfad4a36491fe02a/t/60055b84db80cc1be40800f4/1610963844745/hv_simplicite_regular-webfont.woff2');
} 

Use this CSS

header#header a.btn, h3.portfolio-title {
    font-family: 'HV Simplicite' !important;
}