[SilentSoul]

I have tried this codes for you and worked fine for me,Try to move your codes somewhere else in your script also add return true to avoid unkown command error.

pawn Код:

CMD:aacmds(playerid,params[])
{
    ShowPlayerDialog(playerid,0,DIALOG_STYLE_MSGBOX ,"Admin Commands:","Level 1: /aduty /announce /cc /asay /arepair /jetpack /kick /getip /arepair /warn /lspecoff /lspec\nLevel 2: /explode /slap /ban /freeze /unfreeze /get /goto /mute /unmute /addnos /acar /abike /aheli /aboat /weaps\nLevel 3: /tmenu /poweron[off] /aweaps /setpowerjump /giveweapon /resetweapon /givemoney /superman\nLevel 4: /tmenu /poweron[off] /aweaps /setpowerjump /giveweapon /resetweapon /givemoney /superman\nLevel 5: /setskin /hearnear /freezenear /unfreezenear /healall /armourall\nLevel 6: /akill /setlevel /gmx","Close","");
    return 1;
}

If this didn't work, you should use Strcat