devices on Wifi

A hill you say? Humm that doesn’t bode well. If you have to go to the top of the hill to get 5G service that might just be a rather big problem. I think the house is in the wrong place. 
I live in the western ridge and valley part of the Appalachians and I can see the entire tower 5.3 miles away so it works but hills present huge problems for valley dwellers. An external 4x4 MIMO panel antenna might be your only alternative. Check out Waveform.com for their prices. It is not an inexpensive endeavor but it does help some people. 

Thanks for the advice. It is raining outside so I will have to possibly wait until the weekend to try this. I get 5G as soon as I get to the top of the hill on either side of my house. 

Take the gateway outside and then check the metrics. T-Mobile support can tell you what cellular signaling you should expect. Confirm that the tower you believe to be the source for the network is correct. Yes aluminum siding could be part of the problem. If you are not seeing 5G then you should contact support and get some verification on the cellular signal and location. 

I do not even have any statistics for 5g and I  about a mile from a tower. My house has old aluminum siding and I am wondering if that is hindering somehow. I am thinking a mimo external antenna will help. 

Oh yes, in the “More” section select “Advanced Cellular Metrics”. That will give you the ability to know how the 4G LTE & 5G bands are performing. The 4G is primarily used for signal control and the 5G is carrying the bulk of data load. Try to get the best and cleanest signal quality for the 5G. 
Your location and distance to the nearest cellular signal source may be pretty straightforward but if not then it does take a bit of extra effort and focus to get the best through put. 

You have to be connected to the local wireless network to manage the gateway. It can only be managed by T-mobile engineers from the outside interface. 

Just poke around in the interface and get acquainted with it. If you don’t understand the metrics do a search if need be and understand them. The location of your gateway is important to obtain the best cellular signal strength. Increments of rotation of the gateway can improve reception. Avoid locations where there is metal or appliances. Close to a window is usually better but I have seen reflected signals surprisingly good. Just don’t make blind assumptions. Experiment as needed to get good results. 

At the bottom there is a menu. Swipe to move to the right end of it to “more”. 

I still do not get access to see primary and secondary numbers. Maybe I am not looking in the correct places. 

To get the admin access you need to use the mobile phone app to manage the gateway. The newer T-mobile gateway doesn’t provide web management via a browser.