Hello Samir,
I can work with that message, thanks.
Yes getting started is not easy. Home Automation is a diverse field and you’ll need to get up your system step by step. There is no single video or page because multiple steps are involved and not all of them are relevant for everyone. E.g. most users will already have an MQTT broker set up and running. Hence there is no need to learn how to set one up. That’s why there are multiple resources you have to look into.
- First you should install an MQTT broker and integrate it in openHAB. There is a bullet-proof tutorial over here: MQTT Binding (v1.11) Getting Started 101 - Be sure to also follow relevant links.
- Now you need to flash tasmota to your Sonoff: https://github.com/arendst/Sonoff-Tasmota/wiki/Upload - So far this involved soldering and connecting a serial programmer but it just got a lot easier by the SonOTA method: https://github.com/arendst/Sonoff-Tasmota/wiki/Upload#sonoff-factory-ota-mechanism-experimental - I did not use the method yet but many have successfully and if you need help, you will find tutorials via google.
- Now you can configure the module to connect to your Wifi and Broker. That’s pretty easy and shouldn’t be an issue via the web frontend of the module.
- After everything went well and you’ve got a Sonoff module sending data to your MQTT broker, with this broker being connected with the openHAB MQTT binding, you can set up openHAB items for your module: https://github.com/arendst/Sonoff-Tasmota/wiki/openHAB
And there you have it. Your one single guide to success 
Happy Hacking!