The liability of employee as a bank signatory

I was employed with a company which ran into troubles and stopped paying salaries.

I was an authorized signatory and I had endorsed cheques of a third party to a local bank as a signatory.

The bank filed a legal case against me, the owner of my company and the person whose cheques they are.

It has been 4 months since I resigned, cancelled my power of attorney and mentioned in the resignation to remove my names from all banks.

I have moved on and looking for a new job. I have opened a case against my ex-employer for my salaries and gratuity of 7.2 years.

I have also placed visa cancellation request and I found out about this case when I was moving to my father's visa.

Please advise what I can do, the cheque amount is AED 250k. I need to prove my innocence as I haven't taken the amount nor do I have this kind of amount to pay.

I am innocent in simple words. I was just a PA to the owner and was doing my duties while I was there.