mobile internet issues

Just picked up the T mobile internet and have a few questions

so far been working pretty good but, i have experienced drop in performance and not too happy. 

how can i best use this device to get peak performance? 

where is the best location to put box? 

can you add an attenna? 

can you add the uverse to mesh and provide backup? 

Is it best to put box outside? 

can you even do that?

I heard some people are soldering an antenna?

is there a newer box available?

thanks for help