After getting very helpful replies from Jan Schotte, I try it with a second question:

As shown in the screenshot below, I have a 2D planar form with a round section in the middle. From the left side a heat flux (load) is applied. I try it with the transient (not steady-state). The round part has a slightly higher thermal conductivitiy. I want to see how the heat spreads in the material.

Unfortunately, the simulation stops too early, so the left part is heated, but I cannot see how the heat spreads over the full body. Can someone please let me know which parameters I have to adapt to fully simulate the heat flux?

The data files can be found here:

https://bardhome.de/index.php/s/nRyJjwYTWQbttyN