Pls remove this custom CSS –
@media only screen and (max-width: 767px){
#header .button.get-app {
position: relative;
display: block !important;
top: -25px !important;
float: right;
}}
Instead add the below custom CSS in themeoptions –
@media only screen and (max-width: 767px){
#header .button.get-app {
position: relative;
display: block;
top: -10px !important;
right: 0;
float: none;
margin: 20px auto;
}
.button.get-app i {
display: inline-block;
}
#header {
height: 180px;
}}
Regarding mobile menu you can modify the file header.php line no:62.