# Make the heart of this people insensitive

"Make these people unable to understand" or "Make the minds of these people dull"

# Make the heart ... insensitive

This command means that Yahweh will use Isaiah's message to cause the people to understand even less and to make them less sensitive to what Yahweh is doing.

# their ears dull, and blind their eyes

"make it so that they cannot hear, and make it so that they cannot see." 

# they might see with their eyes, hear with their ears

People being able to understand Yahweh's message and what he is doing is spoken of as if the people were able physically to see and hear.

# understand with their heart

Truly understanding something and caring about what is happening is spoken of as if the people were to understand with their hearts.

# then turn

"follow me again" or "then start trusting in me again" 

# be healed

"I would heal them"