Has the death rate of covid decreased since the start? are doctors better able to treat the disease now than in march?

Yes: Although no consensus exists yet on how best to approach all types of patients, the response to a variety of treatments has been encouraging. Overall case fatality rates are falling, at least in the USA.

COVID 19: A great deal has been learned about the management of COVID since initial onset of the disease. It is hard to compare the actual percentage of infected people who died from COVID 19 or it's complications, since fewer people were tested early in the battle of COVID 19. More asymptomatic or mild cases are likely to be picked up with increased testing.