You can easily calculate how many years of plant growth you need until the damage done today is reversed, and this does not include all future damage.
Humans have added about 700 billion metric tons of carbon dioxide into the atmosphere in the last 120 years. You can look up the yearly mining of coal, lignite and oil since 1900 until today to compare them to the increase in CO2 content in the atmosphere, if you are not sure where this increase comes from. This is equivalent to 270 billion metric tons of pure Carbon. Your average plant contains about 15% carbon. So this amounts to about 1.6 trillion tons of plant mass, which you need to add to the world, just to offset the current increase. All harvests right now on the world amount to about 5 billion tons of plant mass per year. This amount you have to add would be equivalent to 300 years of world harvests, of which none can be used for human consumption, because you urgently need the carbon to stay sequestered.
Additionally, plants growing better in higher CO2 are mostly dicotyledons, while monocotyledons don't profiteer as much. There have been experiments where, depending on the CO2 levels, dicotyledons will suppress monocotyledons at higher CO2 levels, while at lower CO2 levels, monocotyledons outcompete the dicotyledons. Sadly, with the exception of the potato, most of our food providing crops are monocotyledons, like wheat, rice,bananas or corn. Dicotyledons give mostly fruits and some vegetables, but not the starch rich crops, which yield the highest harvests. The same goes for temperature: Higher temperatures are preferring dicotyledons, while moderate temperatures are better for monocotyledons. There is a reason why most food is grown away from the equator in the moderate climate zones, and why the most people are living there.
What you are doing with higher CO2 levels and higher average temperatures is basically killing off all our crops and forcing us to really fast find new, dicotyledon based food sources.
While I agree, that higher CO2 levels will increase plant growth in general, it will not increase the amount of food we can grow. For that to happen, we are planting the wrong crops.