30 ppl party and they want separate bills

Just had the most horrible table in my life. There was a 30 people coming for dinner and each of them ordered different drinks, appetizers, entrees, and deserts. They didn't tell me that they wanted separate bills at the beginning so I only wrote one big bill which is about 1500 dollars. After that they said they wanted separate bills, and some of them wanted to pay for other people, so it becomes like 25 separate bills in total. I went to the manager and her weak ass told me to do whatever they demanded.

The worst part is, the checking system was broken so I have to hand write and calculate each of their bills. It's fucking horrible because later they started to play dumb with me and keep complaining about the bills was overcharged, pretended that they didn't order some of the items. Manager didn't do absolute jack shit so I had to explain their bills, each and one of them. Two of them ran away during the moment and the manager told me to cover 50% of the bills that wasn't collected, which is like 80 dollars in total.

I was absolutely exhausted. I think I'll quit tomorrow.