Well, it's fiction, historical fiction, aka based on historical facts but plays loosely with it.

Is it possible two friends had information that helped turn the war? Another comment said the story was improbable, except in the 1920s students were all wealthy, so a wealthy German spends a couple years at Oxford? Very possible. Made friends with a Brit? Also very probable. Both wealthy enough to be close to the power base but still too young to be directly in it? Very probable too. Each having access to information or persons to tilt the war? Maybe, maybe not.

So it's an interesting story, good script, really good cinematography. One comment compared it to James Bond movies. Perhaps she might need a lesson in who Sir Ian Fleming was during WWII and following Might need to read the books rather than just watch the movies. This stayed more true to a spy novel than some of the movies of the genre have.

I would've said 7.5. Rotten tomatoes says 8.6 (86%) at this time. So I rounded up.