If that is really the first time you have tried it, you are doing very well, and I think it would be a good idea to do much more of it. I can detect a greater degree of natural ease and flow than in the pieces you have posted. Of course, in improvisation, you are not restricted to playing in notational rhythms, because what you play has no requirement to be written out; neither do you have to remain within the style of your pieces unless you choose to. Start from complete freedom and work towards an order of your own making.
Just allocate a certain time to pure improvisation each day, build up your keyboard vocabulary (chords, scales and other patterns), and do plenty of listening. I don't know that classes in improvisation have ever worked very well anyway; one on one lessons with a good improviser, if you can find one, are better.
Improvisation isn't like learning pieces, where you achieve something and then stop. It is a continuous, lifelong process, and you never reach the end of it. I can assure you, however, than if you persist with it, it will reward you greatly in later life, possibly more than any other musical activity.
Topic: My First Improvisation