If you cannot find the exact "Shell Medium" file, these five free fonts offer identical functionality and weight:
body font-family: 'Shell Medium', 'Helvetica Neue', sans-serif; font-weight: 500; Shell Medium Font Free Download
@font-face font-family: 'Shell Medium'; src: url('Shell-Medium.woff2') format('woff2'), url('Shell-Medium.woff') format('woff'); font-weight: 500; font-style: normal; If you cannot find the exact "Shell Medium"
Then apply it: