In the solution are nearly all 10 letters of EINER FEHLT ("one is missing"), but be careful: one is missing!
One further constraint: Only 6 of the 7 following hints are true. You can solve the puzzle with logic, no need for "wild guessing".
1. In every row and every column is one E
2. Two of the columns are completely filled with letters of FEHLER
3. In all fields with odd index number are different letters of HILFE
4. The sum of the field index numbers of all - in the solution - included letters of FIT is 16
5. In field 5 is a letter of FERN
6. The 5 letters of NIETE are all in one row and one column
7. In one row are 3 letters of TEILEN
Solution code: index number of the wrong hint, then the 9 letters row after row from left to right
on 19. December 2020, 02:53 by Ms.Logic-FEAR
Schönes verzwicktes kleines Rätsel :))