best app for remote access large files DL and upload

Hello, im new here, may name is jack. I have a Drobo NAS 5n. I called drobo and asked what the best app for remote access was and they only recommended there built in web based app. While this is okay for random file access, it is not by any means a day to day solution for what we need.

So what we need.

We upload and DL between 5 and 20 gigs of data on any given day. From home where the drobo is located is fine of course but for my employee remotely located its slow and has DL errors.

What would be the best app, or third party app for direct access DL UL that if internet is interrupted it will continue the UL or Dl once back online, handles large data transfer seamlessly, and can auto save to the Drobo when my employee saves to his own drive, like google drive does?

Thanks for your help!