The answer to your first question is Yes, you can do it with the help of translations.
Here is the guide on translations: https://qloapps.com/managing-translations-in-qloapps/
Now coming to the second question regarding the payment gateway,
Yes, we can integrate any payment gateway module to QloApps you required. And it will be a Paid Service.
The cost of the service depends on the efforts required to integrate the payment gateway.
But, we are also running an offer for our customers. If you buy any of our QloApps services billing to a minimum 750 USD in total then we will integrate one payment gateway of your choice to QloApps for free.
You will have to provide the APIs of payment gateway for the integration if they are not open publically. And if the APIs are publically open then please share the link.
Our store has services for many platforms, to avail the offer you will have to make the purchases in the QloApps category only.