mobile captions are too big!

hello

my captions are too big for mobile they have been coded to fade up as per attached. do you know the code I can use to ensure th captions in mobile are smaller centred and without such a gap / leading. if I change the rem 1.6 to 1 the number the caption is too small for the desktop. the coding for desktop is all good.... thank you in advance!

What is site url? We can adjust code easier

hello 

thank you

url is https://flower-harp-kbzs.squarespace.com

but also from a code you sent around the burger I am not able to adjust the padding its very wide can you please help here too? Many thanks much appreciated

div.header-menu-nav-item a {
    font-size: 30px !important;
    padding: 0px;
}

site private