Did you receive a written termination letter, either handed out or sent to you via registered letter?
If no: You are still employed. Do nothing until you receive it, the law is on your side.
If yes: There is a so-called "Insolvenzgeld" every employee who got terminated due to bankruptcy is entitled to. This is regardless of the time you have been with the company, so the regular 12 months employment period does not apply.
Furthermore, check if your company is threatened by bankruptcy or has filed for the opening of bankruptcy proceedings.
The big difference is that in the former case, they are not yet bankrupt and can legally sign a termination. If they are already insolvent, then only the court appointed administrator can do so, unless it's a so-called self-administered insolvency (Insolvenz in Eigenverwaltung). So it's good to double check to know whether the termination is in fact legal and binding.
If you have confirmed that the termination was duly received and legally issued, you must inform the Arbeitsagentur in due course (meaning: less than 14 days upon receiving the letter, ideally immediately) to apply for the Insolvency Proceeds. In that case you must as well inform the ABH without delay; however only after confirming that you have in fact been legally terminated. Don't raise any sleeping dogs otherwise.