Cell phone signal into basment home

My TMoblile gateway is a NOK 5G21.

Knowing I do not get any cell signal in my house I installed a Cell Phone Signal Booster from Amazon (https://www.amazon.com/gp/product/B0BV65DLX1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) I have it wired into my basement home (actually have dirt and concrete roof). 

It sends a signal into my home. My US Cellular cell phone works in all my rooms. And is about equal inside using signal booster and outside with speed tests. 

My TMobile gateway works. But when I take my Gateway out onto my roof, it has a much faster down and upload speed than when it is inside using my signal booster? 

Can anyone help me figure out why my TMobile Gateway is slower inside connected to the booster than outside? 

Gracias,

Jim