How to position OccupancyGrid in RVis - understanding TF

edit

Hi! I've just started with ROS and I need help understanding how TF works.

I'm trying to run this simulation on ROS2 Eloquent:
https://github.com/chapulina/dolly
and I'd like to use SLAM from Slam Toolbox:
https://github.com/SteveMacenski/slam...

The robot has 2 frames:
https://github.com/chapulina/dolly/bl....

  <!-- output -->
  <publish_odom>true</publish_odom>
  <publish_odom_tf>true</publish_odom_tf>

  <odometry_frame>odom_demo</odometry_frame>
  <robot_base_frame>chassis</robot_base_frame>

The robot is positioned at -37 5.6 in the "world":
https://github.com/chapulina/dolly/bl...

<!-- Dolly -->
<include>
  <pose>-37 5.6 0.33 0 0 0</pose>
  <uri>model://dolly</uri>
</include>

When I run slam_toolbox it outputs /map topic with OccupancyGrid messages.
I'm using static_transform_publisher to transform map frame to chassis with all zeroes.

Now in RViz I see all 3 frames in the center of the grid (map, chassis and odom_demo).
I can also see the laser scan results which start from the center of the grid.

However I see the map display way outside of the grid.
I suspect it's because robot position is at -37 5.6, chassis and map are statically linked through static_transform_publisher, which "pushes" map away from center. Here is how it looks(don't have enough point to post an image directly):
https://imgur.com/a/xFMjuOj

What I'd like to see is map being in the center and see robot move on the grid as I move the robot in simulation.
Something like the last gif on https://github.com/SteveMacenski/slam...

Am I correct in assuming that I need:

1. Make map a "fixed frame" in Rviz
2. Somehow make transformation between map and odom_demo dynamic so it would take position calculated via slam_toolbox and transform it to the robot position on the grid.

This way "OccupancyGrid" will stay at the center of RViz grid and when robot moves it will change odom_demo position which will change chassis frame with it.
How do I do that? Does slam_toolbox already have this transformation?
Is this even a correct understanding of what TF means?

Another question:
I've been reading https://www.ros.org/reps/rep-0105.html and I think my frames correspond to:
earth -> don't have one, I've also seen world in a couple of places, how do I create one?
map -> map
odom -> odom_demo
chassis -> base_link

Is this correct?

Thanks!