Why cannot save directly to external SD-USB-ext. HDD with my New HiMedia Q5 Quad?

[AC Question]

I cannot download and save into any of the external memory devices that I pluged to my New HiMedia Q5 Quad , this device is supposed to have 2 GB of RAM and 8 GB of flash memory, but in the first place, it shows only 4 GB of flash memory and it uses most of it for installed applicacions, then what is left is where it saves the dowloaded files, this space is not enough for a movie in 4k UHD and it is required to look for other memory devices,

this device New HiMedia Q5 Quad has room for 3 USB drives one SD card, external. but none of them are visible when downloading or viewing with the file manager app.

Now How can I save movies and other files to the external memory of devices in the New HiMedia Q5 Quad.

Is this impossible?

The device also comes with a SATA cable, but I do not know if conecting a SATA HARD DRIVE to it, would allow to save into from the downloader, can this be done?

Thank youm for your help.

Sincerely

Edwin.