en_tn_condensed/act/28/27.md

For the heart of this people has become dull

People who stubbornly refuse to understand what God is saying or doing are spoken of as if their heart is dull.

with their ears they hardly hear, and they have shut their eyes

People who stubbornly refuse to understand what God is saying or doing are spoken of as if they are unable to hear and are shutting their eyes so that they will not see.

understand with their heart

Here "heart" stands for the mind.

turn again

To start obeying God is spoken of as though the person were physically turning toward God.

I would heal them

This does not mean God would only heal them physically. He would also heal them spiritually by forgiving their sins.