QGIS: prepare data for timeline animation

I have a data-spreadsheet containing a value-attribute that changes over time for a number of administrative units. I have a polygon layer as well with features for each of the administrative units. The spreadsheet containing the date looks like this:

I now want to use the built-in temporal control in QGIS 3.16 to visualise the change of the attribute-value for each administrative unit over time. I imported the spreadsheet as attribute data. Now the problem starts: how to join the attributes to the geometry? Each geometry (administrative unit) should contain for every time-stamp a separate value.

Having the Admin. units in the spreadsheet in the top row, I can’t make a table-join with the polygon-layer. So I tried to first convert the spreadsheet in this way:

No I can joint these attributes using the Ad.Unit-field to the geometries of the administrative units. That works, however, I only get the first data-set per ad.unit (day 1). All the others are left out. But to be able to animate, I should have a value for each day (timestamp-field).

What I would like to achieve is a time-animated circle-marker whose size depend on the value-field for each day. How to achieve this?