In the first and second century, due to wars, all of the trees in the Garden of Gethsemane were cut down. However, olive trees are known to be "immortal". It is very hardy: drought-, disease- and fire-resistant and can live to a great age. Its root system is robust and capable of regenerating the tree even if the above-ground structure is destroyed.
In other words, it is highly likely that the trees currently standing in the Garden of Gethsemane sprung from the same roots as those in the time of Jesus or even earlier!
The word "Gethsamane" derived from Aramaic, meaning "oil press". The oil that it is referring to comes from these olives.
In Matthew 26, Jesus was truly suffering emotionally before the physical torture and agony. Jesus fell on His face and begged His Heavenly Father to remove the cup of suffering from Him.
Yet nevertheless, He did it anyway…willingly.