gate hardware

I have a spring on my wooden gate and it's too loose. It no longer closes the gate like it's supposed to. How do I adjust the spring gate closer so it will close?

I am a landlord and need a lock for a chain link fence. What can you recommend for two swing gates that meet in the middle? Want to lock the two pieces together, however I need tenants to be able to exit from one side in case of fire, want street side to be always locked. thank you