Why two different language in the same receipt

Although the interface language is Turkish, something in Arabic language is written.

The Arabic phrase on your receipt is either the description from the line item or—if no description was entered—the name of the account to which the line item is posted. Neither would be translated by the program, because were entered by the user. The program translates only titles and field labels known in advance. See the Guide: Set language | Manager.

Look at the Edit screen of this receipt. I believe you will see that something was entered in Arabic.