Search bar not displaying on mobile + mobile nav menu customisation

Hi there, Website: www.herhq.net The search bar is not displaying on mobile. I'm yet to discover any answers or workarounds on this forum that resolve this, so would really appreciate some advice. As the website is quite focused on written content it's important viewers can search via mobile. Also, I am hoping to customise the mobile menu colours to match the website (all white background, black text). Thanks in advance!