Reading between the lines, I'm guessing you want something like this:
DELETE
FROM
R
FROM
dbo.trebovnica_roba_roba As R
WHERE
id_fakture = 7
And
rn = 'RN 002 2022'
And
Exists
(
SELECT 1
FROM dbo.trebovnica_roba_roba As R2
WHERE R2.id_fakture = R.id_fakture
And R2.rn = R.rn
And R2.id < R.id
)
;
That will delete all rows for the given
id_fakture
and
rn
other than the one with the lowest
id
.