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Thank you everyone for the input. I have checked all of the suggestions. Unfortunately, I haven't found the movie I'm looking for. However, I like the idea of the character being part of "Special Operations Executive". To be honest, I had no idea this organization ever existed, so thank you KEVP for suggesting it. I have found a bunch of movies and series with characters involved with them. I believe a good contender are the series Secret Army, but it'll be awhile to go through all of them, Secret Army has 43 episodes alone. I've also been looking at smaller nations' productions - Poland, Netherlands, Czech Republic, Slovakia, Belgium, Norway. I'm also looking at WWII movies in general, I have found a lot that didn't know about before.
Soldier of Orange is interesting. There's a scene where the guy sees that those are German planes but kept kissing the girl because he thought they'll pass over them on their way to England but they started bombing around them and that's when they stopped kissing. In any case, the movie/series I'm looking for is newer, has better quality from what I remember. It's also missing the balcony scene. I remember that scene distinctly because when the main character was sneaking on the soldier from above, my dad and my sister said that he'll jump and my mom and I said that he'll simply drop the knife/bayonet. He ended up jumping.
I want to apologize for mentioning the song Caruso. I believe I got confused with the TV mini-series The Fortunate Pilgrim (Italian: Mamma Lucia) with Sophia Loren in the main role. They used the Luciano Pavarotti version of the song and it has nothing to do with the WWII movie.
It cannot be Max Manus since this movie is from 2008, although I did check it out, it looks exciting. I went to college abroad in 2005, so it can't be any movie made after June 2005.
Thank you everyone, I'll keep looking and give an update later.