When changing between the C and D7 chords, do not move your first finger as it is common to both chords. The first finger acts as a pivot around which the other finger s move. This will make the chord changes easier. Practice slowly and evenly and count or tap your foot as you play to help you keep time.
Rhythm Pattern
The following chord progression contains the C and D7 chords. Don't forget to use the pivot finger between these two chords.