The NFC North side replaced their coaching staff at the end of last season, having missed out on the playoffs for the second year in a row.
The new head coach told the Bears' website: "I don't think he's flinched. I just think he likes football. He likes the information. He's working through a lot of different things in terms of the information. We threw a ton of stuff at him [on Tuesday], in our red-zone period, a bunch of new plays.
"We had multiple snap counts [yesterday] throughout practice. Our line was focused, our guys were focused. We did not have a pre-snap penalty today and it was our most difficult day at the line of scrimmage with snap counts.
"I feel there is a comfortability, but a sense of urgency with both of us. I feel like it's open and honest. It continues to grow. We've only laid a foundation here for the last six months. What's ahead will really allow us to grow and test us and I'm excited about that. I think he is as well. We understand what's at stake."
Trestman joined the Bears from the CFL's Montreal Alouettes, where he won two Grey Cups.