This "they'll win anyway" is some miserly nihilistic take - we've won against the Nazis before we'll win again.
"how many times are as supposed to vote to prevent the fascists from gaining power?"
Until you can no longer physically vote.
You are part of a society that still allows you to politically organise around your beliefs, so get involved in your local politics and help bring your vision of a better future to more people - change doesn't happen by itself.
Join a union. Get out there and make it happen.