Employment bond for two years

Hi all, I joined as a software developer trainee in april 2021 with 2.5 years bond period and Before joining that company, they collected my both sslc and hsc marksheet original. After joining in company they are not provided proper training, after joined 7 days they put me in one project. But without training I could not do that project, I asked them to give some time to training, but they forced me to that job only. After a week, I affected by high mental pressure and eye problem, I took 1 week treatment for that but I got eye problem oftenly.So I asked them to relive from job after 3 months, but they denied that. They told me to wait for two month without doing work. In that situation i didn't know what to do. I waited till that 2 months. After I called them, they said me If I quit the job, I have to pay penalty amount. But they did not told me how much amount I have to pay. they told 'After the bond period they will tell how much amount I have to pay and after the bond period they will return my certificates'. Then I quited that job. 1.The bond was not made with stamp paper. In the bond, they are not mention If I break the bond, I have to pay penalty. 2.They not even told me If I break the bond I have to pay bond amount when I am joining. Should I pay them If they asked bond amount.