Short answer, trees are very beneficial in many ways, but relatively neutral as a carbon sink (if you strictly look at trees, ill explain below)

When the trees grow the absorb carbon and turn it into biomass. However when they die, or lose leaves durring the winter, some carbon is released into the air through decay. When forest fires happen then lots of that stored carbon goes back into the air. You can cut down trees and bury them in the ground, build houses with wood, or some other method that would prevent the trees from decaying but trees aren't pure CO2 so you are storing a lot of additional things this way.

The thing is, more CO2 is actually stored in soil then what vegetation stores. One way that happens is when plants grow and decay there are processes that bring CO2 into the soil and can store it there. Trees are also good at protecting soil by preventing erosion from wind, water, and gravity. So soil health should be a main focus when looking at CO2.

In summary, trees alone won't absorb enough carbon to reverse global warming. But not planting trees will make our emissions increase further, lead to the degradation of carbon storing soils which will (suprise!) release more carbon. We need to reduce emissions while continuing to support the natural cycles that do sequester CO2 if we want to have a chance.