Wireless Joint

I recently received a ATT Netgear Aircard 770S Hotspot. I connected my laptop to the hotspot and internet works great. Speedtest download speeds range from 35-50 down. 10-16 up.
I want to setup my Linksys WRT1900AC router as a WiFi repeater. (I think)

I set my router up as a WiFi repeater. I set it to use the hotspot as the WiFi to be repeated. Router is approximately 2 feet away from the hotspot. So signal is strong. With my laptop directly connected to the router, I get pretty decent speed on the speedtest for downloads. But upload fails.. If I disconnect my LAN from the laptop and log into the router wirelessly, connection is strong. Even at 50 feet away.
Although the WiFi connection is strong to the router, there is no internet at all on download or upload.

Am I missing something? Does my router require a special firmware? Consider me completely green when it comes to networking.. Any help is greatly appreciated.

Broke my prepaid att Zte Blade Spark that i had an unlimited prepaid att mobile plan with that I set up with a VPN and used as my home internet connection to my routers.Trying to get directions or help with setting up my new to me used Netgear aircard 770s with the prepaid unlimited cell plan sim card from my broke prepaid at&t Zte Blade Spark.

Thanks in advance