They must have forgotten to fit the turbo to your bike as well as mine
Seriously, most who can consistently average 19mph are young, fit guys who train hard and consistently.
Afraid, if you are anything like me it is something to be admired and, yes slightly envious of, but it is just not going to happen to a 54 year old menopausal woman
You will still make improvements though......give it time. When I started end of August last year my first few rides were around 14 miles at barely 12mph and I thought 20 miles sounded a huge distance. Now, I regularly do anything between 20 and 50 most mornings and I'm starting to get averages between 14.5mph to just over 15mph on a good day. Whether I can make any further progress remains to be seen but I am reasonably happy so far.
Stick in there.