This probably has to do with the fact that the Mx 5.18 release introduced NavigationLayouts rather than the previously used Layouts module.
What you need to do is select the correct layout (something along the lines of sidebar_full_responsive
in the NavigationLayout module) for error 1. This can be done in the Properties pane which appears on the right hand side within the modeler when you view the page that is generating the error.
I believe Error 2 should automatically resolve after that.
Also refer to the documentation