Problem with Type I Model 9

Greetings from Argentina, I have an issue with a Walther pistol, the pistol does not fully cock and the trigger does not move when I put it on fire, I can't disassemble it because the part in the back appears to be broken, I took it to a gunsmith but he told me the gun had no fix, perhaps the forum can help me. It belonged to my great grandfather who bought it in the 1920s. Excuse my bad English and thanks in advance.