Valley Forge was actually not a battle. It was where the Americans set up their camp for the winter. More than 1/5 of the American troops die from disease and not getting enough food. Valley Forge was very difficult for them due to little supplies and harsh winter temperatures.
The First Continental Congress is the meeting that the colonists had in Philadelphia, Pennsylvania where 56 representatives attend. There was a debate on what they should do about the British overwhelming taxes. They made a list of rights to send to the king and they will meet again if the king doesn't agree within a year.
The Second Continental Congress is the meeting the colonists had in Philadelphia, Pennsylvania after the battle in Lexington and Concord. They were debating on how to react to what happened in Lexington and Concord. They ended up deciding on not breaking away from Britain yet. They made the Continental Army to defend them and put George Washington in charge of it.