The [OPENROWSET documentation][1] describes the `SINGLE_CLOB` option as:

> returns the contents as a **single-row, single-column** rowset of type varchar(max)

So you will either need to split the string into multiple columns using the [`STRING_SPLIT`][2] function (or a similar method), use a [format file][3] to specify a row terminator for `OPENROWSET`, or use [`BULK INSERT`][4], which allows you to specify a row terminator without the need to create a format file.

For example, you could adapt the following code by customizing the `FIELDTERMINATOR` and `ROWTERMINATOR` as necessary for your input file. For example, the following code was tested on [your provided sample file][5]: 

	CREATE TABLE #bulkInsert (col1 NVARCHAR(MAX) NULL)

	BULK INSERT #bulkInsert
	FROM 'C:\Temp\myfile.csv'
	WITH (FIELDTERMINATOR = N','
		, ROWTERMINATOR = N'0x0a' /* See https://stackoverflow.com/a/26758288/1582862 */
		, BATCHSIZE = 50000
		, TABLOCK
	);

	-- The sample rows were correctly bulk loaded, including the header row,
	-- which you can remove from your file or filter out after bulk loading
	SELECT *
	FROM #bulkInsert
	--Nummer
	--072XXXXXX63
	--072XXXXXX76
	--07XXXXXX66
	--072XXXXXX4


  [1]: https://learn.microsoft.com/en-us/sql/t-sql/functions/openrowset-transact-sql?view=sql-server-2017
  [2]: https://learn.microsoft.com/en-us/sql/t-sql/functions/string-split-transact-sql?view=sql-server-2017
  [3]: https://learn.microsoft.com/en-us/sql/t-sql/functions/openrowset-transact-sql?view=sql-server-2017#input-file-format-options
  [4]: https://learn.microsoft.com/en-us/sql/t-sql/statements/bulk-insert-transact-sql?view=sql-server-2017
  [5]: https://gist.github.com/pattertall/dd8ff283ee3a7900b043993d917c3537