1. Add this CSS below (In this article you can find information how to add custom CSS to any WordPress Theme: How to add CSS code that is future update compatible)

@media (min-width: 768px) {
.mh-search-horizontal .mh-search .mh-search__element {
width: 50%!important;
}
}

@media (min-width: 1023px) {
.mh-search-horizontal .mh-search .mh-search__element {
width: 25%!important;
}
}

2. Edit page

3. Edit search form and set "Number of filters to show before the "Advanced" button" to 4

5. It will look like this