what did gene believe finny was trying to do

I'm not sure at what point at the story that you mean so I'll guess Chapter 4. Gene, an academic perfectionist, laments his poor performance on the test to Finny; Finny mocks Gene's ambition to be first in their class, and Gene begins to believe that Finny doesn't want him to do well in school, so that he will come out ahead. This is an excerpt from GradeSaver. Check out the source link below.