If you can not even find a gui for QoS of any kind you likely can not. Even if you could it takes a very advanced QoS configuration to solve your issue. Most routers that have QoS can only limit the upload....ie data you send to the internet. People seldom overload the upload bandwidth so this feature is of little use even on routers that have it.
On the download side when the connection is overloaded the ISP has decided which traffic to delay or drop. By the time your router gets involved nothing can be done. Pretty much all solution use the download QoS setting to trick end device into requesting data at a slower rate. It does not always work though.
On top of all this the device you are using runs on LTE broadband...