Change the color of lines and it will fixed.
Alternatively share you store url an I'll try to post the solution in next reply.
Note: If your store is not live and passwords protected then share password too.
This is an accepted solution.
You are using Font Awesome Icons but library is missing in the template.
To fix it, add this line
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
before </head> tag in theme.liquid, you can find this file under Layout
Once you do it you will find in parallel to hamburger menu, cart icon will also appears. Also other icons which is missing in you template will start working.
But it's also better if you save this css file in your assets and call through directly instead of using hotlink.