Responsive full website using Css, flexbox, Js and HTML

Hello friends, if you notice on the mobile dropdown, i used a darker shade for the dropdown background. this is because when i initially used the "backdrop-filter" to achieve the frosted glass effect, i realized that it worked on my chrome browser but some browsers did not support it hence they just showed a plain background. I would like to ask for alternate suggestions on how to achieve the frosted glass effect that has more support range. Thank you.