Every run you do will be challenging from wk1 r1 to wk9 r3 (graduation) but every run you do will strengthen you just that little bit more ready to face the challenge of the next run.
Pace/speed is not something you need to worry about at this time as slow is the key, slow helps build strength in not only your muscles but also the tendons and joints (particularly in your feet) which helps to prevent injuries.
Also it's not about the speed/distance that you achieve (this will come later) but it's about running for the required times ,so you run as slow as you need to to do this (sustainable pace)
You are on a journey to a new you, an adventure of a lifetime so enjoy people for it truly is life changing.
Happy running