will the chinese embassy in dhaka be closed on 2,3,4th april?if so can we apply for visa on 5th?

Yes, the China emabssy is closed on 2,3,4th April, and you may apply for the visa on 5th.
Please note the Office Hour of the Consular Office are:
Counter Time: 9:00am - 12:00pm, Sunday through Thursday except on holidays
Telephone call: 15:00pm - 17:00pm, Sunday through Thursday except on holidays