Hi,
What is your website URL? Are you using Woocommerce for shop?
Ideally it should allow users to add products to cart and "Continue Shopping" or move to "Checkout". At checkout page, user should be asked to login/register to continue.
I can work and fix this for you.
I am available on Chat if you want to discuss project details.
About Me:
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My name is Imran and I have been working as a HTML/CSS/PHP/Wordpress Developer, Designer and Coder for the last 8 years. I have earned 333 positive reviews from my previous clients on Freelancer.com with an overall rating of 4.9/5 stars. 100% of my projects were completed on time and on 99% on budget with 27% Repeat Hire Rate. You can check all this on my profile page here:
https://www.freelancer.com/u/imranphp.html
Thank You and Good Luck for your Project.
Imran Ali.