Want my website to be mobile friendly

Hi there,

Not tech savy in the least, so building my e commerce website has been to put it mildly… a challenge. I chose this theme because it said it worked well with mobile devices. However in my shopping cart, under calculate shipping (so my local customers can pay by cash, upon pick up and skip shipping costs) the fields for country, province and postal code are almost completely gone~vs on the computer they show up perfectly. How can I fix this so customers can input shipping info (for local pickup) while using a mobile device.