Is it possible to add a separate seller login in wix website for Allowing Others to Sell Products on Your Site ???
You will have to look at making up your own site for selling.
https://support.wix.com/en/article/request-creating-a-classified-ads-site
Check out these old posts.
https://www.wix.com/corvid/forum/community-discussion/can-users-submit-and-sell-products
https://www.wix.com/corvid/forum/community-discussion/how-to-make-classifieds-site-using-wix-code-showcase-tutorial
https://www.wix.com/corvid/forum/community-discussion/classifieds-searching-for-a-solution
https://www.wix.com/corvid/forum/community-discussion/like-a-classifieds-page
Please note that with the above links, Andreas has not been connected with Wix now for a good while, so you will not got any reply if you try to contact.
Depending on what you are wanting to sell, you can always filter like this example.
https://www.wix.com/corvid/example/mega-search
https://www.wix.com/corvid/example/real-time-notifications-for-real-estate
For the different options of buyer and seller etc, you just give them different member roles of buyer and seller.
So when the user logs in you can check the member role and do whatever for a buyer or a seller etc.