Hi Tsania, welcome back to the community.
since openmc has said that there are overlapping cells in Universe 4 (cells 11 and 12), you can investigate those cells.
I usually check my geometry.xml file to find which regions that overlapping each other in my cells because I can see the cell ID in geometry.xml and find which part of my model has the wrong region definition.
I think these tips can help you
https://docs.openmc.org/en/latest/usersguide/troubleshoot.html