LCD Wrong Characters

i'm very young in the world of Arduino and i'm having a serious problem with the LCD QC2004A and Arduino Mega because whatever i write in alphanumeric, is translated to chinese language and i really don't know what to do to change it.

I have already searched in too many websites and i saw nobody who has already discovered the solution for this thing.

As you can see on the figure bellow, the diference between the chinese alphabet and alphanumeric is only the first number of the upper 4 bits which is responsable for the alphabets is always "1" and i don't know how to put it in "0".

Table 4 Correspondence between Character Codes and Character Patterns (ROM Code: 0A)

I believe that DB4 is responsable for this number, but i don't know.

Is there any way to change the state of a DBx in the LCD, maybe try to define this DBx to be always 0 ?

I tryed to connect on the ground but it did not workd

Solution

Telling from this QC2004A datasheet your display uses a KS0066-compatible display controller which in turn should work with any HD44780 LCD software library.

If all 8 data lines (usually pins 7-14) on your LCD are connected, make sure your display library is configured for 8-Bit mode.
If only 4 lines (pins 11-14) are connected, then double check that your software is configured for 4-Bit mode.
If you are able to read what you expected the LCD to display by changing Bit 7 (not Bit 4) on each character (using your character table and a piece of paper), your software library might need to be configured to use the latin instead of the kana character set.
If that manual translation does not yield anything comprehensible, double check your wiring especially on LCD pins 7-14 (or 11-14 for 4-Bit mode). The IO pins on your arduino might be placed out of order.
If the text on your display is mixed latin-kana, you might be using the wrong ROM Code A00 instead of A02 (see HD44780 datasheet table 4).
If all that fails, try another LCD software library to rule out software issues.