It's particularly difficult in the beginning... so don't get discouraged.
I just started at Planet Fitness, too! 2 hours is a long time to spend at the gym, so I would definitely aim for 30-45 minutes of cardio, plus some of the strength training. And like others have said, change up what muscle groups you work on from day to day. Also, after a bit of time of doing this (several weeks), you may want to change to treadmill for cardio.. you don't want to get "used" to one type of cardio.
Great job and keep up the great work!
And as EagleRiverDee just said, work up to this in stages. When I began, I could only run a mile in 15:30-16 minutes. Today I ran 2 miles in 24 minutes. You'll get there, just give it time! :-D
