override one of the existing function, how to handle the rest of the function?

HI I was reviewing the code.
Does :void mean ignore this function in my override?

example:

private function clearIndexTable(): void

When I do override, I copy the original file and modify. The original file has few functions, I only need to modify one of the function. So how do I handle the rest of the functions that doesn’t need to be override? I did try to delete those functions that doesn’t need to make any change and it breaks. Please help and suggest me what I can do.