What is the time that is needed for a 75 years old man to be cured from covid 19 in a hospital ? ?

There is no way to determine this ahead of time.  Every patient is different and will require an individualized treatment plan.  Recovery depends largely on the person's immune system responses...please speak with that person's doctor to find out how long his/her hospital stay might be.  The doctor and/or nursing staff should be able to fill you in on the status of your relative.  Random strangers online cannot render any realtime medical information.

Some people recover within a couple of weeks, others have problems for months.  In Spain, a lady of 113 seems to have had little problems and just isolated until she had a negative test.  In the USA, a 6 week old baby died. A woman in her late 50s spent 131 days in hospital. There is no set time. 

give em a few weaks he shoul be fixed up for ya by then