I need help badly!

I will try my best to not cry at this moment as I am writing this. On June 13th, I was going on a vacation to Athens Greece leaving IAD to YUL and then from YUL to a direct flight to Athens Greece with my children. The flight was Air Canada and United. It was a total of 7 tickets. The return was same. Athens Greece, to Montreal (YUL) and then from Montreal to (IAD). The flight from IAD was delayed due to mechanical issues. This caused us to miss our flight out of YUL and we were transferred 4 times in getting to Athens. Each flight we missed of which they needed to reroute us. We arrived in Athens 10 hours after our scheduled time of which we missed the first day of our tour. Not only this, but we lost our luggage and had to spend the next two days shopping to get clothes rather than enjoying the city. The return was worse. The flight was delayed due to mechanical issues and each flight after was delayed due to mechanical issues which was stated on the notice, they gave us. It took us a total of 96 boarding passes and 12 flights to try to get home. This included an overnight hotel stay in Montreal of which Air Canada refused to assist with. After the airline continually bouncing us in the air. They stated they did not have a flight out of Boston for 4 days. I then decided to purchase southwest tickets to get my family home of which cost another $3,000. In addition, the luggage was lost again, and we still have not retrieve any of the luggage lost from the first trip nor the second. I filed claimed as instructed and 15 days later, I received a letter stating that the cause of the delays was due to Covid-19 and they will not reimburse anything from the flight. I lost over $16k in expenses. This does not include the cost of the initial luggage lost. But now, I am stuck paying credit card bills for clothes and items that it was not my fault for loosing. Is there anyone I can call or write for assistance?