This blog article outlines how to react if your template gets corrupted after you have added an image to the header. If you face this problem, please try to restore it and set the following setting for the picture in the header:
With a right-click on the picture, select the
❶ Size and Position Settings. In the so opened Layout settings, please navigate to the
❷ Text Wrapping-tab and select
❸ “In line with text“.