Too hard for you, since he would have illegally held the office he can't be removed from it, merely declared ineligible to be the president. There are plenty of posts on this thread tha will help you, if you are having trouble understanding the issue.
I'm not the one having trouble understanding the issue. And I'm apparently one of the few who has actually read the Constitution. Obama is president. If he is found to be ineligible then he's removed from office and Biden is president. What part of the 25th Amendment is so hard for you to understand?