If you put some kind of items into the dumpster, then such dream signifies your desire to get rid of negativity in your waking life. If you are doing it secretly, you are trying to avoid the duties that should be done by you. The dumpster could also denote to the fact that you are not loving yourself enough and see that you are not worth good things.
Dream dictionary: Dumpster dream meanings
Seeing a dumpster in dreams is usually an announcement of the arrival of a period with many serious disorders that will be particularly unfavorable.