Half of my map is 1000s of meters to low.

I am totally new here and I am sure I did something wrong. But when I reopened my project today half of my map is 1000s of meters lower then the rest. See pic. Is there an easy way to fix this

If you don’t use version control, check your Saved/Autosaves folder in your project’s folder. Replace the map with an autosaved version.