You can find documentation in here https://payeer.com/ru/

You can like this listen Plugin events and expand functionality

<?php
use RainLab\User\Models\User as UserModel;
use Shohabbos\Payeer\Models\Transaction;
use Shohabbos\Portal\Models\Payment;
Event::listen('shohabbos.payeer.existsAccount', function ($id, &$result) {
    // find order or account
    $result = UserModel::find($id);
});
Event::listen('shohabbos.payeer.checkAmount', function ($amount, $currency, &$result) {
    // check amount
});
Event::listen('shohabbos.payeer.saveTransaction', function ($postData) {
    // save transaction
        $transaction = new Transaction();
    $transaction->m_operation_id = $_POST['m_operation_id'];
    $transaction->m_operation_ps = $_POST['m_operation_ps'];
    $transaction->m_operation_date = $_POST['m_operation_date'];
    $transaction->m_operation_pay_date = $_POST['m_operation_pay_date'];
    $transaction->m_shop = $_POST['m_shop'];
    $transaction->m_orderid = $_POST['m_orderid'];
    $transaction->m_amount = $_POST['m_amount'];
    $transaction->m_curr = $_POST['m_curr'];
    $transaction->m_desc = $_POST['m_desc'];
    $transaction->m_status = $_POST['m_status'];
    $transaction->save();
});
Event::listen('shohabbos.payeer.successPayment', function ($id, $amount, $currency) {
        // add balance or check order as paid
    $user = UserModel::find($id);
    $user->balance += $amount;
    $user->save();
    // add to history payments
    $payment = new Payment();
    $payment->user_id = $id;
    $payment->is_buy = true;
    $payment->amount = $amount;
    $payment->payment_system = 'payeer';
    $payment->date = date('Y-m-d H:i:s');
    $payment->save();
});