Site Optimization not working on mobile

Site URL: http://www.nirbhaykuppu.xyz

Hey guys, so I've run into a little bit of an issue. I just created a website which works well on PC. 

However when I open it on the phone the images don't resize to fit the screen, they are all stretched and weird.

Also when i open my website up it shows up as an non secure domain, and its red. Any ideas how i can solve this stuff?

Thanks so much

Nirbhay

With non secure domain, enable SSL:  https://support.squarespace.com/hc/en-us/articles/205815898-Understanding-SSL-certificates 

@media screen and (max-width:640px) {
.index-item-width-full .index-section img {
    width: 100% !important;
    left: 0 !important;
    height: auto !important;
}
.homepage article.index-item.has-item-image {
    height: 20vh;
}
}

Thank you sooo much, you're awesome!

Any suggestions you might have for the website are welcome!

@tuanphan the thing is all my images changes resolution and also the Commercial section changed isnt working properly now. 

@tuanphan im not able to understand why the commercial page is displaying wrong on mobile. www.nirbhaykuppu.xyz/commercial

@media screen and (max-width:640px) {
.index-item-width-full .index-section img {
    width: 100% !important;
    left: 0 !important;
    height: auto !important;
}
/* homepage */
.homepage article.index-item.has-item-image {
    height: 20vh;
}
  /* Commercial */
body#collection-5ec7632ada11085700454c35 article.index-item.has-item-image {
    height: 15vh;
}  
}