Seems you might need to look at a Landing page as a precursor to your shopping cart.
There is a wealth of info on creating landing pages - search for 'landing page that require account registration to continue'
Here's on article
https://www.crazyegg.com/blog/landing-page-essentials/To the best of my knowledge no such feature exists within AbanteCart or any of the MarketPlace extensions at this time.
If you are wanting a customer to be registered with a particular language coming up to that account - the only way I think that can work is to use multiple stores setup - and set a language to each store - and then direct that customer account to that store URL.
Otherwise the customer needs to select their desired language from the drop down offered on the site.