ok I found very usefull at https://www.paypaltech.com/PDTGen/,
but one thing I dont get it: where do you setup the first page where you put amount?
like for ipn the button?

hier is what I did till now:
at https://www.paypaltech.com/PDTGen/ I generated code for soundbox and that's for redirect page:
"SO I NEED THE FIRST PAGE TO MAKE THAT BUTTON with price, HOW DO I SET THIS UP"

<?php
// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-synch';

$tx_token = $_GET['tx'];

$auth_token = "my token";

$req .= "&tx=$tx_token&at=$auth_token";


// post back to PayPal system to validate
$header .= "POST /cgi-bin/webscr HTTP/1.0\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
$fp = fsockopen ('www.sandbox.paypal.com', 80, $errno, $errstr, 30);
// If possible, securely post back to paypal using HTTPS
// Your PHP server will need to be SSL enabled
// $fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);

if (!$fp) {
// HTTP ERROR
} else {
fputs ($fp, $header . $req);
// read the body data
$res = '';
$headerdone = false;
while (!feof($fp)) {
$line = fgets ($fp, 1024);
if (strcmp($line, "\r\n") == 0) {
// read the header
$headerdone = true;
}
else if ($headerdone)
{
// header has been read. now read the contents
$res .= $line;
}
}

// parse the data
$lines = explode("\n", $res);
$keyarray = array();
if (strcmp ($lines[0], "SUCCESS") == 0) {
for ($i=1; $i<count($lines);$i++){
list($key,$val) = explode("=", $lines[$i]);
$keyarray[urldecode($key)] = urldecode($val);
}
// check the payment_status is Completed
// check that txn_id has not been previously processed
// check that receiver_email is your Primary PayPal email
// check that payment_amount/payment_currency are correct
// process payment
$firstname = $keyarray['first_name'];
$lastname = $keyarray['last_name'];
$itemname = $keyarray['item_name'];
$amount = $keyarray['mc_gross'];

echo ("<p><h3>Thank you for your purchase!</h3></p>");

echo ("<b>Payment Details</b><br>\n");
echo ("<li>Name: $firstname $lastname</li>\n");
echo ("<li>Item: $itemname</li>\n");
echo ("<li>Amount: $amount</li>\n");
echo ("");
}
else if (strcmp ($lines[0], "FAIL") == 0) {
// log for manual investigation
}

}

fclose ($fp);

?>

Your transaction has been completed, and a receipt for your purchase has been emailed to you.<br>You may log into your account at <a href='https://www.paypal.com'>www.paypal.com</a> to view details of this transaction.<br>