In short: Yes, you can eat out while using the app. However, it depends on your priorities and goals.
If it is your goal to reach a desired look within a given time frame, eating out may not be the best idea for you. Meals at a restaurant are hard to track and hard to guess for their nutrient and calorie content. Once sure won't hurt but eating out every day will not get you the results, trackable meals will.
If you are training for general well-being, treating yourself to a nice meal at a restaurant is part of it. However, for general well-being and health, you should also eat clean. Therefore, eating out too often is not advisable.
