TelegramBot Webhook已设置，但不起作用

I have some questions about setting the Webhook in TelegramBot. At first I followed a YouTube tutorial. I hosted free webspace at lima-city.de (lang-DE) with an SSL certificate and set the Webhook with https://api.telegram.org/bot183900136:AAEk7QYske1vtpl9GlR_-7KMye2g6jMfynQ/setwebhook?url=https://telegram-bot.lima-city.de/helloworld.php

Is used the following code:

$botToken = "MyBotToken";
$website = "https://api.telegram.org/bot".$botToken;
$update = file_get_contents("php://input");
file_get_contents($website."/sendmessage?chat_id=217296540&text=hi");

But my Bot doesn't react to my messages. Here are some tips from TelegramBot:

1. You will not be able to receive updates using getUpdates for as long as an outgoing Webhook is set up.
2. To use a self-signed certificate, you need to upload your public key certificate using certificate parameter. Please upload as InputFile, sending a String will not work.
3. Ports currently supported for Webhooks: 443, 80, 88, 8443.

I don't know what I could do next to solve the problem.