Thanks for replying to my question guys, it really helps me understand this.

Still I have some things that I dont understand:
- How do you know you have enough time for the transfer; for example you planned 2 hours for your transfer, but your first flight is delayed for 3 hours.. Is there some kind of guarantee or cashback if these kind of things occur?

- How do you know the value of the miles you for a certain flight. For example, in the article explained above, the guy said this too: I try to book milerun flights if I get around 5(!) times the value of the ticket, in miles. For example: if he books a flight for 200euro, the value of the miles he gets should be around 1000 euros.

I understand this theory, but how does he know the value of the miles is around that 1000 euros? (and is this even possible nowadays?)

- When I look around on this forum I see alot of people talking about a flight and then they add a certain Fare behind it. For example V fares. What do these characters mean and what how can I use/learn about them?