Call a locksmith
Landlords are legally required to provide a secure lock to any external entrance. Typically, crime prevention recommendations by police suggest that external wooden doors need to be solid timber, with a five-lever mortice deadlock two-thirds of the way up. UPVC external doors should also come with a three-point multi-locking system.
Doors are only as strong as their weakest point, so it might be worth installing a metal bar on the hinge side to reinforce the door – known as a Birmingham bar. On the side where locks have been fitted so wood has been removed, consider adding a London bar to help prevent splits at that point if someone attempts to kick the door in.