Question: How did the girls survive for five whole years in an abandoned house in the woods? Did Mama help them to survive by giving them things to eat like cherries?
Answer: Yes, Mama kept them alive. We see a wild apple rolling across to the floor to the huddled girls, implying that Mama gave it to them, and would have continued to give them forest fruits. She undoubtedly also showed them where to find water.
Answer: I'm pretty sure that they ate cherries because of all the pits shown when the two men enter the house. They probably ate other things as well because Lily is shown eating a moth in one scene.