Sunexpress Baggage Issue: Lost Items and Lack of Support

I flew with Sunexpress flight XQ799 from Düsseldorf to Kayseri on July 29, 2024. The 20:55 flight was delayed by an hour. Upon arriving in Kayseri, I couldn't find my luggage. I filled out a form at the airport and left without my suitcase. It's now August 1st, and no one has contacted me. I've never seen such an indifferent company. I'm a student, all my clothes are in my suitcase, and my summer school has started. I have books in there, and my classes are disrupted. How can a company be so unresponsive? I called Sunexpress in Kayseri, and they said the issue is in Düsseldorf and that they would contact me. Shame on you, Sunexpress. Furthermore, their phone lines are unreachable. What's the point of 4440797? Sunexpress is a regret.