At the start of his jump the air resistance is small, so he accelerates downwards.
As his speed increases his air resistance will increase
Eventually the air resistance will be enough to balance the sky
divers weight. At this point the forces are balanced so his speed becomes constant
Terminal VELOCITY
When the parachute is opened the air resistance suddenly increases,
causing him to start slowing down
Because he is slowing down his air resistance will decrease again until it balances his
weight. The skydiver has now reached a new lower terminal velocity