THY Benelux Tour Issues, Flight and Baggage Problems

I purchased a Benelux tour from Kappa Tourism for the dates 20/07/2024 - 27/07/2024. The tour program included a flight to Luxembourg first. Due to a system error, I couldn't complete the online check-in for our 07:10 Luxembourg flight with PNR number V64FP5, so I arrived at Istanbul Airport at 03:30. However, THY did not process our check-in. They claimed the ticket was not mine and that I couldn't fly, putting us in an overbooked situation. They attributed the issue to a system error and did not address our grievances. The supervisor repeated the same statements without offering any solution. We spent hours trying to explain ourselves, stating that we had tried online check-in 24 hours prior and that the issue was not our fault, but they did not care. They said there was nothing to be done and that the only possible solution was to go to the gate and wait, hoping for a no-show or to pay extra for a seat. Exhausted from explaining myself, I took the standby ticket and waited at the gate but couldn't board the flight. Due to THY, I was separated from the tour group, which was against the rules, and we learned that there were 29 more passengers than seats on the plane. Seats were sold to multiple people, and those who paid more got to fly. It seems I couldn't convey that I was a tour passenger. My long-planned program, motivation, vacation, and energy were ruined. The program was to start in a few hours, but I was still at the airport and couldn't fly. No one took responsibility, listened, or cared. After waiting for a few hours, THY arranged a flight to Paris with the tour representatives. We didn't sign anything, only gave verbal consent as we were convinced it was the best option at the time. We were exhausted from explaining ourselves. We arrived in Paris around 14:00. Our luggage did not arrive with us. We spent hours dealing with that issue as well. Hunger, sleeplessness, and fatigue no longer mattered; we waited for hours, and the luggage finally arrived on the 20:00 flight. It was like a nightmare, and my luggage was broken when it arrived. Our airport transfer was not arranged either. The tour company had already completed the transfer with the other participants, so they didn't come back for us. We had to make our own way and missed the first day of the tour program. I faced a series of problems one after another. Despite all these issues, THY did not hear us, care, or take responsibility.