1. present simple
1.1. verb
1.2. when to use it
1.2.1. fixed (von außen festgelegt) (timetable, schedule)
1.2.2. The train leaves at 8.45. The plane arrives at 20.05. The test is on Monday.
2. present continuous
2.1. am/is/are & verb-ing
2.2. when to use it
2.2.1. appointed/arranged (ausgemacht) We are going to the cinema tonight.
2.2.2. instead of "going to go" "What are you going to do?" – "I'm going jogging."
3. will
3.1. will (not) & verb will not = won't
3.2. when to use it
3.2.1. quite certain (sicher, gewiss) Most people will drive electric cars in a few years.
3.2.2. less certain key words: think, maybe, probably, ... I'll probably become a mechanic. (Vielleicht werde ich ein Mechaniker.)
3.2.3. spontaneous decision (spontane Entscheidung) (In a restaurant, looking at the menu): I'll have the roast pork.
3.2.4. formal style The meeting will begin at 10.00 am. The president will give his speech at 4.00 pm.
4. going to
4.1. am/is/are (not) going to & verb "gonna"
4.2. when to use it
4.2.1. individually planned, intention (Absicht) This weekend I'm going to do nothing.
4.2.2. predictable (vorhersehbar) Look at the clouds! It's going to rain soon!
4.3. was/were going to & verb
4.3.1. was planned but not accomplished (geplant, aber nicht durchgeführt)
4.3.2. I was going to phone you, but I completely forgot about it.