I want to look at the code of a certain app, without modifying it. Is that fine accordingly to EU laws ? Btw, sorry if I posted this in the wrong place.
Yes. Even if you needed to break an encryption scheme or blow-up a protective box, it's your right to take anything you own apart or reverse engineer software algorithms.
Be careful, however, about using anything you learn. For example, don't sell copies if there are patents, don't use knowledge of the innards or knowledge of software keys to circumvent security/safety. And, you might want to keep what you've learned secret to avoid enabling others to do anything similar. For example, don't publish (e.g., on Youtube) a nuclear bomb teardown, or a new analog descrambler teardown, or MP3 bits, or the source code for software. Even if software is free, many license agreements will prevent you from distributing it, just like a copyright.