Yes you can change your shop products by using shopify backend.
I suggest, before doing anything, learn the market as it becomes easier for you to identify the target customers and then draft an effective marketing strategy which may help position your business among the target audience.
I just reviewed your store and I think you should do some improvements on your store rather changing the products. You just need the effective marketing strategy for your business, also there are many technical errors on your website that you need to resolve.
Create a strong brand presence on social platforms:-
Whether you know or not the presence on social platforms are a big deal. Being active on social media help create a sense of credence among people. people love to buy form shop or store that they are familiar with, a good online presence on social platforms like Facebook makes it quite easier. You can never ignore social channels if you are venturing into the digital world. I would suggest to create a Facebook page to display your items and to share them in Facebook groups. Invest your time researching different ways to create a strong digital presence.
The key to success is always keeping up with the current trends, no matter the amount of experience you have. Actively read blogs on jewellery industry, look for inspirations on social media and don’t stop expanding your knowledge.
Also consider these few minor things to make your store better:
Adapt Mobile First Strategy: Make mobile your first priority. Check everything on your mobile first from structure to design, check each and every element of your website on mobile view as more than 90% of internet use is expected to come from mobile devices only.
Speed - To increase visitors and sales you need to work on your website performance’s speed as I am seeing it is very slow. It should be above 80%. Also, you need to optimize website images. It will improve the user experience. Fast page load time will also boost the website’s crawl rate.
Put Effort Into Online Reviews & Social Proof: Social media Makes your visible and it expands conversion such as Facebook, Twitter, Pinterest and Instagram are great platforms for marketing and connecting with customers.Also, add favicon on the website.
Footer: You need to add proper footer menu links. Also, you can show website information and address in the footer.
These few tweaks can really benefit your store and improve your sales, I hope my feedback will help you!!! If you have any questions, don’t hesitate to ask!!
In regards to changing your online inventory, this jewelry specific app (https://apps.shopify.com/jewelry-store) connects suppliers to retailers on Shopify. You can change and add inventory to your store to increase you customer base and sales.