At this point you decide fundamentally how your course should be structured.
The choice depends on your teaching concept: select the topic or the week format and organize your content accordingly either by topic or by week. In the grid format, images can be inserted for each topic to help navigate to the topic.

For those in a hurry: leave the default setting “theme format”.

In week format still set the start date with “course start”.
In Topic format your course consists of (automatically) numbered topic blocks.
Advantage here: No adjustments need to be made if topics are postponed or cancelled. Combine the grid format e.g. with the course layout “Only one section per page”.

Here you can set the number of weeks/topics.
Remove excess, empty topics or add new ones as needed. On the course main page, the plus/minus icons perform this task.

• Overview of course formats Moodle Tip: Making courses learner-friendly (Tabea Reimitz, TU Darmstadt, 2/18/20)
• Course formats (moodle.org)