If you're in a run and die it's usually best just to start over from the beginning of the game, not only because you lost the upgrades to make the bosses easier but also because of the massive time you would save by not dying. The game is relatively short and more practice by replaying all the levels is only going to make you a better speedrunner/player. I always wanted to keep runs alive after I died, but it was usually best to just forfeit it and try again lol. I wish you all the best.