How can i be a better goalkeeper?

i trained with my club and got better and now the season is finished and we are goin into the preimer league next season and we will have to be better but i want to practice at home to get better but i need to get fitter and have better reflexs any tips? p.s there is another goalkeeper there and is no.1 so i want to come back and be better than him.At the moment im playing handball to help my reflexs