Black stool, vomiting. Of my brother.

One of my cousin brother age 35 from 25th of this month he is passing black stool,vomited and weakness of the body so we have taken him to the primary health centre and they have admitted for 2 days and on that day they have given inj  zanocin,inj tramazac, inj pan IV,inj ondem,inj botropase,RL and syrup sucral o and yesterday they have discharged and for five days they wrote the medicine i.e Tab Bacterie oz,Tab panicare d,Tab Trapic 500 and sir even now not fully recovered,so dear sir may I know the causes for this problem and what are the foods that he needs to avoid.and yesterday he feels much better but from today afternoon suddenly he feels weakness and mild fever also loss of appetite.So can I give him paracetamol now as he is having mild fever and can I give glucon D as he is having loss of appetite.what can be the problem of my brother.waiting for valuable answer.Thank you sir