Update language_de.h

Addition of missing strings to match language_en.h

Marlin/language_de.h

 #define THIS_LANGUAGES_SPECIAL_SYMBOLS      _UxGT("ÄäÖöÜüß²³")
 
 #define WELCOME_MSG                         MACHINE_NAME _UxGT(" bereit")
+#define MSG_BACK                            _UxGT("Zurück")
 #define MSG_SD_INSERTED                     _UxGT("SD-Karte erkannt")
 #define MSG_SD_REMOVED                      _UxGT("SD-Karte entfernt")
 #define MSG_LCD_ENDSTOPS                    _UxGT("Endstopp") // Max length 8 characters
 #define MSG_PREHEAT_1                       _UxGT("Vorwärmen PLA")
 #define MSG_PREHEAT_1_N                     _UxGT("Vorwärmen PLA ")
 #define MSG_PREHEAT_1_ALL                   _UxGT("Vorw. PLA Alle")
+#define MSG_PREHEAT_1_END                   MSG_PREHEAT_1 _UxGT(" Extr.")
 #define MSG_PREHEAT_1_BEDONLY               _UxGT("Vorw. PLA Bett")
 #define MSG_PREHEAT_1_SETTINGS              _UxGT("Vorw. PLA Einst.")
 #define MSG_PREHEAT_2                       _UxGT("Vorwärmen ABS")
 #define MSG_PREHEAT_2_N                     _UxGT("Vorwärmen ABS ")
 #define MSG_PREHEAT_2_ALL                   _UxGT("Vorw. ABS Alle")
+#define MSG_PREHEAT_2_END                   MSG_PREHEAT_2 _UxGT(" Extr.")
 #define MSG_PREHEAT_2_BEDONLY               _UxGT("Vorw. ABS Bett")
 #define MSG_PREHEAT_2_SETTINGS              _UxGT("Vorw. ABS Einst.")
 #define MSG_COOLDOWN                        _UxGT("Abkühlen")
 #define MSG_FILAMENT_CHANGE_OPTION_HEADER   _UxGT("ÄNDERE OPTIONEN:")
 #define MSG_FILAMENT_CHANGE_OPTION_EXTRUDE  _UxGT("Extrude mehr")
 #define MSG_FILAMENT_CHANGE_OPTION_RESUME   _UxGT("Drucke weiter")
+#define MSG_FILAMENT_CHANGE_MINTEMP         _UxGT("Min. Temperatur ist ")
+#define MSG_FILAMENT_CHANGE_NOZZLE          _UxGT("  Düse: ")
 
 #if LCD_HEIGHT >= 4
   // Up to 3 lines allowed
   #define MSG_FILAMENT_CHANGE_INSERT_1        _UxGT("Filament einlegen")
   #define MSG_FILAMENT_CHANGE_INSERT_2        _UxGT("und Knopf")
   #define MSG_FILAMENT_CHANGE_INSERT_3        _UxGT("drücken...")
+  #define MSG_FILAMENT_CHANGE_HEAT_1          _UxGT("Knopf drücken um")
+  #define MSG_FILAMENT_CHANGE_HEAT_2          _UxGT("Düse aufzuheizen.")
+  #define MSG_FILAMENT_CHANGE_HEATING_1       _UxGT("Düse heizt auf.")
+  #define MSG_FILAMENT_CHANGE_HEATING_2       _UxGT("Bitte warten...")
   #define MSG_FILAMENT_CHANGE_LOAD_1          _UxGT("Warte auf")
   #define MSG_FILAMENT_CHANGE_LOAD_2          _UxGT("Laden des")
   #define MSG_FILAMENT_CHANGE_LOAD_3          _UxGT("Filaments")
   #define MSG_FILAMENT_CHANGE_INIT_1          _UxGT("Bitte warten...")
   #define MSG_FILAMENT_CHANGE_UNLOAD_1        _UxGT("Auswerfen...")
   #define MSG_FILAMENT_CHANGE_INSERT_1        _UxGT("Laden und Klick")
+  #define MSG_FILAMENT_CHANGE_HEATING_1       _UxGT("Heizen...")
   #define MSG_FILAMENT_CHANGE_LOAD_1          _UxGT("Laden...")
   #define MSG_FILAMENT_CHANGE_EXTRUDE_1       _UxGT("Extrudieren...")
   #define MSG_FILAMENT_CHANGE_RESUME_1        _UxGT("Fortsetzen...")