Employer not return my original educational certificates

Sir,i joined the new company april-23 ,i joint before MD got my original BCA And MCA Certificates provisional marksheet for security reason at the time i had a critical situation so surrender my certificate to them ,still now i not get any offer letter from them but starting time they said 3 month has a notice period with out offer letter,but i said them when i start the work 1 or 2 months then satisfy i can continue the job ,otherwise i leave the job so only hope to surrender my certificates to them but (management irregular activities and employees handling (spoke vulnerable)all are fear to work with them now i got a new offer letter from new company with good salary, offer letter received after i inform to MD i got a offer letter i wil joint new company 45days after i train the any employee with in this period everything said clearly to them ,that time our md accepted all,but last one month till now no one appointed this post,today i met and inform to our MD with in 10days i releave from here they not accepted whatever say,they said hold your salary and sure not given your certificates 90days notice want to complete then only confirm it,but my position worked old employeehe was also frusted to wquitjob here (MD given a pressure ,hold salaries,Vulnarable words,and beat him)right now i am in same sutiation so pls help to resolve the matter and how to get my certificates and salary smoothly from them