1. Open the the wp-config.php in the WordPress root directory and check that the DB_CHARSET is defined to UTF8:
12/** Database Charset to use in creating database tables. */define('DB_CHARSET', 'utf8');
2. Go in your database and check that the charset of your database and all your tables is UTF8:
If everything looks OK but the problem is still there, we recommend that you report your issue on the specific language forum to know how native speakers handle these characters.