I'm 19 years, my tall is 160, my weight is 90kg and my blood type is o+. what's the best weight for me? what should i do to make my weight is good?

Looks & feels right: Thanks for writing. Blood type has nothing to do with ideal weight despite what anyone else may have told you. In fact, "ideal weight" is subscience, since your total weight that you can modify is a function of your muscle mass and body fat. The truth is that your best weight is what looks and feels right to you, and with which you are able do well in vigorous physical activities that you enjoy.