Opel Agila A rear lock no longer works

Hello, I’m new here on MotorTalk and would be happy about help.I drive an Opel Agila A Color Edition red Built 08/2001 1.2l 16V 55 kw approx. 70000 km. Now I have the following problem. For a few days I can no longer open the tailgate. If I put the key in the lock and turn is no sound to hear and the lock does not unlock. In the meantime I had removed the inner cladding of the tailgate and tried to open the lock via the bars, a About it doesn’t work. Does anyone have an idea how to open the tailgate without leaving a big batch of money at the FOH? I thank you in advance for your help. LG