"You still waste time with those things, Lenu? We are flying ..." — Elena Ferrante quote meaning

You still waste time with those things, Lenu? We are flying over a ball of fire. The part that has cooled floats on the lava. On that part we construct the buildings, the bridges, and the streets, and every so often the lava comes out of Vesuvius or causes an earthquake that destroys everything. There are microbes everywhere that make us sick and die. There are wars. There is a poverty that makes us all cruel. Every second something might happen that will cause you such suffering that you'll never have enough tears. And what are you doing? A theology course in which you struggle to understand what the Holy Spirit is? Forget it, it was the Devil who invented the world, not the Father, the Son, and the Holy Spirit. Do you want to see the string of pearls that Stefano gave me?