As a teacher,what do you do if you were required to finish multiple tasks by the end of the day, and there was no way that you could finish them?

Prioritise! Do what I could and if it appeared that my workload was going to continue along the same lines I would have to look carefully at how I worked or at how the "system" expected me to work. At least one of these things is wrong and needs to be put right if I am to continue as an effective and responsible teacher.