Hi Marcel,
This is because there are duplicate Display Names of Account fields.
Note that the imported template cannot have duplicate column names, which is the Display Name of the fields.
So we have to find out the duplicate Display Name.
Go to https://make.powerapps.com/, select the D365 environment and go to Data > Entities > Account > Fields, sort by Display name and try to find duplicate fields.
If there are too many fields, then you could click Edit data in Excel to download the Excel file.
Here is a demo, I changed the display name of the field "Twitter" to "Facebook", then there are two "Facebook".
In the Excel, these two fields are displayed as "Facebook" and "Facebook2".
Therefore, the column of the duplicate field will end with 2.
So wo search "2" in the Excel and find all, we will see the duplicate field.
Go back to power apps, edit the duplicate field and change its display name.
