remove all FAQ without your FQA file from disk and to make english default and olny one enable for forum, you should edit editdisplay.tmpl and:
find<select name = "chosenlanguage" class="formboxes">
<option value = "english" $english>{$ubbt_lang['L_ENGLISH']}</option>
<option value = "big5" $big5>{$ubbt_lang['L_BIG5']}</option>
<option value = "chinese" $chinese>{$ubbt_lang['L_CHINESE']}</option>
<option value = "danish" $danish>{$ubbt_lang['L_DANISH']}</option>
<option value = "dutch" $dutch>{$ubbt_lang['L_DUTCH']}</option>
<option value = "french" $french>{$ubbt_lang['L_FRENCH']}</option>
<option value = "german" $german>{$ubbt_lang['L_GERMAN']}</option>
<option value = "hungarian" $hungarian>{$ubbt_lang['L_HUNGARIAN']}</option>
<option value = "italian" $italian>{$ubbt_lang['L_ITALIAN']}</option>
<option value = "norwegian" $norwegian>{$ubbt_lang['NORWEGIAN']}</option>
<option value = "polish" $polish>{$ubbt_lang['L_POLISH']}</option>
<option value = "portuguese" $portuguese>{$ubbt_lang['L_PORTUGESE']}</option>
<option value = "romanian" $romanian>{$ubbt_lang['L_ROMANIAN']}</option>
<option value = "russian" $russian>{$ubbt_lang['L_RUSSIAN']}</option>
<option value = "spanish" $spanish>{$ubbt_lang['L_SPANISH']}</option>
<option value = "swedish" $swedish>{$ubbt_lang['L_SWEDISH']}</option>
</select>
change for<select name = "chosenlanguage" class="formboxes">
<option value = "english" $english>{$ubbt_lang['L_ENGLISH']}</option>
</select>