Responsive Sunnyside Agency Landing Page

Hello everyone! I've just finished this challenge but still found some issues with my layout :

1. On my nav::before, the triangle shape in my nav on mobile layout. Seems like it's not very neat if you zoom in that thing but when I see that on the desktop layout it's neat

2. When I see my gallery images (the position is above the footer) in my default browser on the mobile which is Mi Browser the images stretch out on their height but when I see that on chrome the images look fine don't stretch out

Could you help me to find the solution? thanks in advance