Help! MacBook doesn't boot properly after battery swap

HELP, I swapped the battery as described by the instructions, step by step. Don't follow the guide, removing the motherboard is way to risky… I now have apparently damaged the logic-board (according to apple genius). When I try to turn on the macbook the initial loading-bar takes way longer and at about 3/4 the screen shuts off. Does anyone know where ì could look for help or what to do?

Additional information:

- if I boot to the bootcampscreen (pressing r) the display doesn't die, until I actually try to boot…

Is there a way ì can save my beloved mac? Thanks for any help.