How to save a record if I dont want all fields saved?

you have to remove your pass encoding from beforeSave, just do it when you are creating a user

$record = new \MyApp\Models\User();
$record->name  = $name;
$recod->pass = md5($pass);

//if it is possible stop using md5, in controller : $this->security->hash($password); ... more information you can see here https://php.net/manual/en/function.password-hash.php

it would be too easy like that, and in addition new record can be created by 1000 places, and its easy to miss the md5 encoding

you have to remove your pass encoding from beforeSave, just do it when you are creating a user

$record = new \MyApp\Models\User();
$record->name  = $name;
$recod->pass = md5($pass);

//if it is possible stop using md5, in controller : $this->security->hash($password); ... more information you can see here https://php.net/manual/en/function.password-hash.php

class users {

    public static function createUser($data, $pass){

        $user = new \MyApp\Models\Users($data);

        $user->password = md5($pass);

        if ($user->save() === false){
            return $user->getMessages();
        }

        return true;
    }
}

$check = users::createUser(['name' => 'koko', 'age' => 16], 'mypass');

if ($check !== true){
    foreach ($check AS $message){
        // display error messages
    }
}

or you can move the messages logic inside the function, depens of how do you structure your app

mmm nope, got it

function beforeSave(){
    if ($this->id == null){
        $tthis->password = md5($passowrd);
    }
}

or use beforeCreate

https://docs.phalcon.io/en/latest/reference/models.html

As an aside... md5 is easily cracked. Why are you not using the security password hashing built into Phalcon?

The best way to prevent the problem when you have blank password ow you wish it updated only when its set

class Users extends Model
{

    public function setPassword($password = null)
    {
        if (!$password) {
            $this->skipAttributes(array('password'));
        } else {
            $this->password = $password;
        }
    }

    public function beforeSave()
    {
        $this->password = sha1($this->password);
    }

}

in this case when form sets password as blank, becouse it's not changed model set it to be skipped ;) or you can add this skip in initialize and when it's set remove it from skip