Isn't this day light robbery by German government ?
No, since the German government doesn't recieve the money at all (it only gives a financial garantie).
Do you recommend any service from Germany who can help me getting back money to India ?
Yes, contact the Deutsche Rentenversicherung - Beitrags-Erstattung that recieves the money.
This will only be generally possible if no treaty exists about the transfer of pension contributions between the 2 countries.
You can apply for a Versicherungsverlauf, which will list all of your contributions which may be usefull later.
It seems that a treaty with India exists (see page Deutsche Rentenversicherung - Homepage - Arbeiten in Deutschland und in Indien).
The information there also suggests that applications for refunds (if you are eligible, which seems to be possible under certain conditions) can be made directly at a German consulate.
Having the Versicherungsverlauf when contacting the consulate would simplify any application, since all relevant information is contained in the document.
Also why I don't get my employer's contributions as my employer has paid to the government on my behalf, if I wasn't working then my employer wouldn't have paid to German government.
The employer didn't pay on your behalf, it's part of their contribution to the pension system.
Any refund will be based on your contributions, not thoses of others.
Note: The Online services assumes your present address is known.
If this is not the case, fill out and send back the pdf form V0150 informing them of your present address. The PDF contains all possible addresses. Choose the one nearest to where you lived last.
A short letter, with the above information, asking for a Versicherungsverlauf will result in one being sent back to you.