Sounds like you are doing just great for a newbie if you are doing about 14mph

Leg speed is a trained thing - it is very important - so don't give up if you cant spin at 110 right away. Try to do it for just a short portion of the time you are doing those bursts and slowly you will work your way up to it.

There are tricks to leg speed also. If you have a nice round spin, i.e feel like you are wiping your feet off on a welcome mat on the bottom of your stroke and moving smoothly over the top of your pedal stroke, it is easier to spin faster. So work on that and the speed will come. Try just a little bit less resistance too. If you are trying to train leg speed, trying to do this at a high resistance is counterproductive.

You're doing great and your working hard at it. So, enjoy all your milestones, small or large!