The text is in Excel right above the -0,002 - you can see a fraction of the text in the upper screenshot.
It seems that Power Query imports a column from Excel as decimal if there is no text in the first 8 rows. By that, all texts below row 8 gets removed... before there is even a step to convert any types.
I guess the English translation for "Buchhaltung" would be "Accounting", i.e. the number formats that gets all the currency signs left aligned in the cells?
I tried to reconstruct your issue, but no success: data type is based on the first 200 rows. If there is only text in the first 200 rows, it becomes text in Power Query, otherwise any (mixed data), Int64.Type (for whole numbers) or number (for numbers with decimals).
You might consider raising an issue with Microsoft.
I am having a similar issue. Using BPI desktop, when I import an excel "Table", not sheet, I lose the currency formatting and the cells are changed to decimal. Becasue PBI only lets you format one column at a time it would be a nightmare to approach it from that angle. Is there a setting I can look at so I do not lose my excel formatting during import?