Playing guitar is a physical event, we all have different bodies and different flexibility.
C and G7 first, Steve has said that he'd wished he hadn't put it first when he wrote the course, but with that said,
Session 1 was designed to get you used to moving your hands as a group, since they're not used to moving like this.
Not necessarily to "master" these chords, you'll be playing them for a long time. (Hint C G and D seem to make up soooooo many songs)
You'll find many chords/notes are not always played with the tips of your fingers,
You can adjust the neck of the guitar up like a classical player like Liona Boyd or sling it near your knees like Slash,, all is good.
Also angle of your hand will adjust up/down and left /right and can twist as well to reach the chords/notes.
As a warm up start before playing, put first finger down on first fret play note, then 2nd on 2nd fret play note , 3rd of 3rd play note, 4th on 4th, play note. Leaving the prior finger on the fretboard.
Don't need to be fast, don't force, but try.
Then move up to next string etc.
Over time you'll notice more chance of getting the notes as your hand stretches out
until