Normally when you open the bonnet on your car, you pull the release latch located on the interior driver's side. Sometimes the release latch can break or stick. The bonnet release cable can break or seize. There is a method to open the bonnet when the latch is broken.
When you pull on the bonnet release latch and it retracts normally but the bonnet does not open, your latch is jammed or broken. Ask someone to pull up on the bonnet while you pull on the release latch. If the bonnet does not open, you can rule out a jam in the mechanism.
Use a flashlight to illuminate the latch under the front of the bonnet. Take a long tool such as a screwdriver and manipulate the latch until it releases. Have someone put gentle upward pressure on the bonnet while you are doing this to prevent the spring-loaded latch from snapping shut from the weight of the bonnet.
While you are poking around under the car bonnet with a screwdriver, be very cautious about what you touch. Sensitive parts such as the condenser coil for the air conditioning unit may be within your reach. Puncturing this or other components can be costly to repair.