All this soft food does eventually end up on the floor of the cage in large stools. If you clean your mynahs cage daily, you will have no problem. I have put several layers of newspapers separated by waxed paper in the bottom of the cages. This way I can lift out a layer a couple of times a day and have fresh clean papers below. If left for more than a day, a mynah cage can begin to smell.
Mynahs are highly intelligent birds.
They are also highly skilled talkers. When a mynah speaks, it speaks very clear, unlike some birds that talk more muffled, such as cockatiels. My first mynah had a vocabulary of over 150 words. He also spoke in sentences. Not all mynahs develop large vocabularies.