To be specific, growing the types of trees we would want for such a thing in such an amount that it would deal with the problems we have, assuming we stop growth of CO2 and assuming we stop burning the Amazon, would take around a hundred years.

https://www.nationalgeographic.com/environment/article/how-to-erase-100-years-carbon-emissions-plant-trees

"It could take more than a hundred years to add enough mature forest to get sufficient levels of carbon reduction. Meanwhile 40 billion tons of carbon dioxide (CO2) from burning fossil fuels are being added to the atmosphere every year, said Glen Peters, research director at Norway’s Center for International Climate Research."

And need an area the size of the United States. I wasn't joking about a second Amazon.