Flippant answer above, now for a serioius answer.
The population is growing too fast, and we are getting very good at keeping people alive into old age, and keeping alive those babies born prematurely. We can also cure more illnesses.
But the problem is that we do not have one world government who can make the rules for the world.
Individual countries have their own agenda. Get richer, get more luxury goods, more holidays, so each country wants to increase its population to make more money.
It could be argued that the "west" are doing more damage to the world than the so called poorer countries.
I heard that the USA consume half the worlds resource.
Keeping alive groups of people in Africa or India who probably live a simple lifestyle is not the problem, it is the West that is the problem.
We produce the pollution, concrete over fields to make cities and roads, destroy the habitats for wildlife, dam rivers and flood huge areas, make GM crops.
I am not sure of the answer, but I do feel afraid for the future of the world.
I remember the science fiction film Soylent Green with its awful view of future. People living in cars, no fresh food, anarchy on the streets, voluntary euthenasia.
In the end people were eating tablets, and their favorite were green ones (Soylent Green). They were made out of the dead bodies of humans who had died.
Unless we do something we are heading that way.