You can check this documentation below and set the mobile logo height

https://www.joomshaper.com/documentation/helix-framework/basic

For logo you can also try this CSS solution, insert this CSS in your custom.css file

@media (max-width: 991.98px){
#sppb-addon-516c4cba-81f4-4192-92b3-1f11c216a51d img {
    height: 70px;
}
}

And please give me a screenshot of that button which you are talking about.