Special character problem

I created an Hungarian Opencart hompage. Everithing good, but after I make a new account, in my account the name and address datas not correct. The hungarian special characters disappear. If I click to 'Your personal Detals" and rewrite all name and address data, the hungarian special characters appear. But in "Edit your account information" window I cant show hungarian characters. If I rewrite all texts, all special characters lost.
I tried modify the database in myphpadmyn...
I found in /system/library/request.php an entry, .. $data = htmlspecialchars($data, ENT_COMPAT, 'UTF-8') ...
If I change it to "...htmlentries..." a littlebit better. Some special character shown, but I cant write 32 chars.
I hope I will get any help. Thank you.