We use the Present Continuous for future actions which I have already decided and scheduled with certainty. So you can use Present Continuous in example 1 and 2. We use the Present Simple for future actions which are scheduled and decided by someone else, or follow a timetable. For example we say "my train leaves at 7am", not "my train is leaving at 7am", because the train timetable was NOT my decision. Other examples: "the film starts at 8" and "next semester finishes in October". So, if you are taking a train or other timetabled public transport, I would use the present simple in sentence 2. If you are driving yourself, I would use the Present Continuous.

I recommend English Grammar in Use by Murphy for basic grammar topics. The various ways to express the future are covered in units 19-22. For careful English, the present progressive can express a scheduled future event that is not a regular event. For example: “I am taking my brother to the train station tomorrow morning at 6:30.” The simple present can express a scheduled event for transportation. For example: “My brother’s train leaves tomorrow morning at 7.” Of course, English Grammar in Use provides more details. Here is a useful summary of about 10 ways to express future actions: https://www.ef.com/ca/english-resources/english-grammar/future/ [excerpt] Arrangements: I'm meeting Jim at the airport. Time-tabled events: The plane takes off at 3 a.m.

Thanks;)

In the first sentence, both options are equally valid. This is maybe a slight difference in nuance, but they are basically interchangable. In the second sentence, I would say leave/are leaving are interchangeable and arrive is (slightly) preferable to are arriving. Hope that is helpful.