cross icon on mobile menu (to go back) – need to change the colour to white plea

try this in quick css:

.html_av-overlay-side-classic #top .av-burger-overlay li li .avia-bullet, 
.html_av-overlay-side.av-burger-overlay-active #top .av-hamburger-inner, 
.html_av-overlay-side.av-burger-overlay-active #top .av-hamburger-inner::before, 
.html_av-overlay-side.av-burger-overlay-active #top .av-hamburger-inner::after {
    background-color: #fff;
}

and if you like to see the “bullets” a bit more intense play with the opacity:

.html_av-overlay-side-classic #top .av-burger-overlay li li .avia-bullet {
    opacity: 1;
}

what do you have against shortening hexcode according to the nomenclature?
i use nearly almost for code the code tag here on board – that copy&paste will be easy.
#fff is similar to #ffffff (by the way 6digits) – on your code there are 5 !
#3a7 ist similar to #33aa77 etc.
by the way : all three digit hex-codes are websafe colors.

very important: and on your quick css you do not close the media query rule above:

@media only screen and (max-width:767px) {
  #top #wrap_all .av-burger-overlay .av-burger-overlay-scroll #av-burger-menu-ul li a {
    font-size: 20px;
    color: white !important;
  }
#menu-item-search a:before {
  color:white !important;
  }
}

that last curly bracket is missing – and makes all rules later not working ( that is the reason for not having the wider content of 1310px but to have 1010px)