Nick here from Shopify.
Something to remember with all websites which are on Shopify is that they are all mobile optimized so you don't have anything to worry about there. I took a screenshot of your store on my iPhone to show you what it looks like when it is mobile optimized:
The content team at Shopify wrote some blog posts about mobile optimization which might help develop an even further optimized mobile website. You can read it here. There is another helpful guide written by a Shopify Partner which explores some other mobile optimization tactics for you to consider, which you can read here.
Hopefully, this helps and answers your question.
All the best, Nick
1st of all Thanks
2nd I'm checking my Store score on GTMatrix and it is showing one url : https://cdn.shopify.com/s/files/1/1977/9453/files/Home-Slide-1_%7Bwidth%7Dx.jpg?v=1569061470
and I'm lost from where I can find this and remove
No problem at all. Regarding your question, can I ask what you mean exactly by the GTMetrix showing one URL? I'm not 100% clear on what you mean by it's showing.
The link currently shows a broken page (seen below in the screenshot) which looks like it is coming from the files section based on the URL.