This is a company that is growing very rapidly, and the support/administrative staff is too small to keep up with all of the company's needs. While this is something that is recognized and steps are being taken to remedy, right now, there is always way more work to do that can be realistically accomplished. You HAVE to good at prioritizing or you will become overwhelmed quickly.
I would like to add my manager understands this challenge and I have never received any kind of negative feedback due to having many tasks still "in progress"