Two-source hypothesis

The Two-source hypothesis is a hypothesis that was made in the 19th century. It tries to explain what is called the synoptic problem in Christian theology. This problem is that certain parts of the gospels of Mark, Matthew and Luke have texts that are very similar. The hypothesis claims that the Gospels of Matthew and Luke were written based on the gospel of Mark, and lost source text, called Q. The Q is for German "Quelle", and means source. The lost document was likely a collection of Jesus' sayings, very probably written in Ancient Greek. The hypothesis is widely accepted among Christian scholars.
Problems.
There are two major problems with this hypothesis: