My question is, does the pope ever add anything new for christians to practise, or do they stick to wahtever is in the bible. are there any pope’s in the past that passed laws that were created by himself?
They cannot add or take away anything from divine revelation–however, part of divine revelation includes Jesus commissioning Peter and his successors to govern the Church. This requires rules–what we call ecclesiastical or canon law. It’s mostly organizational and so that we may better live the Gospel (rather than giving a different one).
For example, Scripture tells us fasting and worshipping God are good things, so the Pope and bishops have prescribed fasting days and liturgical rubrics so that we have unity in these things.
I hope that helps a little!