What prevents eating outside the home?
People often misunderstand "proper nutrition". Correct means balanced in micro- and macronutrients + sufficient amount of fluid and fiber.
Shawarma is a healthy diet, for example, if it is well prepared. In any restaurant, you can find something that fits into the concept of "right".
Look for dishes that contain proteins, fats, slow carbohydrates and fiber. Caesar, shawarma, salads in canteens, falafel, thick soups ... well, at worst, kefir with banana in the store.
In short, it's absolutely not a problem. Finding what's related to proper nutrition is easy. Next, your task is to eat in moderation and monitor fluid balance.
It should be based on where you eat and what kind of food. What exactly do you mean by proper nutrition, what goals do you pursue.
If, in general, it is possible to answer the question - in theory. (I know people who do not mind.) In practice, it will depend on your desire, money. In a more or less normal cafe / restaurant, you can find on the menu a not too fatty piece of meat or eat a Caesar salad and do not take carbohydrates for dinner (rice, potatoes). I think there shouldn't be any problems with breakfast. But whether you can eat what you need, and not what your friends / colleagues eat, it's a matter of motivation and understanding why all this is needed.