In this video I teach a quick riff in thumb position. It's a simple pattern that repeats in half position so you can practise your shifts between the two positions. It also includes several chords so is a nice way to practice your intonation as you will really hear if there is any problems with tuning as the notes ring out. If you do have issues the first thing to check is your hand shape, particularly the spacing between your thumb and 1st finger. I recommend practising chromatic scales to help you solidify the finger spacing.