The next song has two chords, the C chord and the D7 chord. As there is a D note in both chords, you can keep your thumb on it when you change between the chords. This will make changing between G and D7 very easy.
Instead of writing a sharp sign before every F note on the staff, it is easier to write just one sharp sign after each clef. This means that all the F notes on the staff are played as F#, even though there is no sharp sign written before them.