How to remove sub category in product url and to set only single URL for a single product.

in my website my product access with 3 URL :
https://www.mywebsite.com/root_category ... oduct-text

https://www.mywebsite.com/sub_category/ ... oduct-text

https://www.mywebsite.com/my-product-text

I want URL ​to open with only :

https://www.mywebsite.com/root_category/my-product-text

There's no setting to do this in OpenCart, it's just how it's designed. However, it does use a canonical meta tag in the header, so Google will see the base URL for the product (without any category portion) and know that it's the same page. The URL is also used to generate the breadcrumbs in OpenCart, so if you remove those then the breadcrumbs will only show the root category in the URL.

If you really want to make that change, you'll either need to find an extension that can do that, or hire someone to make that kind of modification for you. If you need to find a developer, you can post a request in the OpenCart "Commercial Support" forum, which is checked by a number of OpenCart developers. You can also try checking out the OpenCart "Partners" area.

I am having the same type of problem with SEO.
I have sub categories within categories and although each page physically works, Google sees them as canonical. The sitemap generated by opencart does not list ALL pages within my site.
example: my site is: autoandmarine.com.au
Google sees all the following pages, all are the same product, but my sitemap lists only the top line;
https://autoandmarine.com.au/Auto-Wire/ ... -Auto-Wire
https://autoandmarine.com.au/Single-Cor ... -Auto-Wire
https://autoandmarine.com.au/2mm-6amp-A ... -Auto-Wire
https://autoandmarine.com.au/Auto-Wire/ ... -Auto-Wire
Currently Google has thousands of my pages listed as canonical and although there may be a fix I have not come across it yet.
Graeme