You're haven't really got the wrong bike...it should be OK but as always the more you spend, the better the ride should be.
As an example, I started on an 8 (16) speed, steel framed heavyweight budget bike. It was a blooming good bike, I did many thousands of miles on it and got very fit.
Then I brought a light Bianchi, 9 (18) speed, a much better bike, twice the price of my first heavyweight....did I go any faster...no. But the quality of the ride was so much better, shifting smoother, less gaps between gears etc etc...just all round better but you gotta pay for that...and you still won't go much faster.
Your bikes fine as a starter IMO.
Check the basics...tyre pressures correct ? Under inflated tyres drag you down.
Better tyres roll better, you will have budget tyres on it, good tyres would improve it, something like Gators perhaps.
Saddle the right height ?, too low, your thighs are going to scream in protest.
Ultimately, get the miles in, it will come.