Reviewing the first step

Ok, I finally found some more time to write.

So did you try the first improvisation? It's time to review.

Which are the expected results? Basically the most important dividend is to feel the time as you play. After some practice you should feel that what you play just "flows" with the underlaying rhythmic pattern. This pattern doesn't have to fight with your melody, it should support it.
The simple melody exercice serves this mainly: to start improvising in time.

Of course it is also possible to improvise melodies with no tempo at all, like recitativo melodies. Or it is possible to just play long chords, in an ethereal way... But this is better done AFTER one masters improvising at a given tempo.

So repeat the melody exercise until you feel confortable about the tempo. Improvising takes time, so just play some minutes per day in the beginning stages. Don't rush... Progress will follow...