Air carrier Ramp Agent reported being assigned the transfer of a large amount of freight; AOG items; and Dangerous Goods in an unrealistic time period. Reporter further stated that the lack of proper time to prepare resulted in a dangerous situation and improper cargo handling.

Narrative

I was directed to work inbound Aircraft X for my first assignment at approximately XA:45; scheduled for a XB:40 arrival. Without any telephone conversation to notify me of the change of assignment; I was given Aircraft Y outbound at XA:05; less than one hour before departure. 5 units of Mail Freight and AOG items were planned; as well as Dangerous Goods. I was also informed after the event occurred of a previous cancelled outbound from the night before; and forwarding of bags from that previous flight that was supposed to be conveyed to me by the Management Team. This did not happen.The Manager changing this flight and the assignment transfer clearly led to the inability to properly and safely plan and negated the per-departure team meeting and huddle. It was a poor decision. I later found out that the trip was originally assigned to another crew minus a crewmember and short-staffed. The Manager could have added these crewmembers to assist with the heavy outbound payload.I informed the Overnight Manager of the heavy bag count and he told me nothing of the additional bags added to the flight. I informed him of the size of the Unit Freight and that there would be no room to accommodate. He said nothing to inform me otherwise.[I suggest] proper preparation and release of the assignment in adequate planning time. Not less than an hour before departure. I worked the same flight 24 hours earlier and it was released one and one-half hours prior. Suitable preparation time allowed me to accommodate previously refused freight from the day before. Proper planning and timely release of assignments is critical to a successful safe and on time departure.