Siebe said: “I also do not understand, when parinibbana is not the end of a being, why is the Buddha not clear about this in the sutta’s?”
I know that you have read a lot of suttas. So. it is surprising that you have not grasped the critical aspects of them. You seem to tend to read suttas and try to ignore the important parts of them OR may be the translations are very bad.
For example, in the Jata Sutta (SN 7.6), it says: “..Yattha nāmañca rūpañca,
asesaṃ uparujjhati” which means that nama rupa are removed without trace for one upon Parinibbana. Nama rupa are the combination of the five aggregates. When they are removed cittas cease to exist.
In the Ratana Sutta (Snp 2.1): “Nibbanti dhīrā yathāyaṃ
padīpo” which means “An Arahant goes out like a lamp goes out”.
I don’t remember the name of another sutta, where the Buddha asks Vaccagotta what happens to a fire when it is extinguished: “Does it go to the North or South? Can you say where it is gone?”. It just does not exist any more.
There are many suttas that discuss Nibbana along those lines.
It is a good idea to read relevant posts at the site before asking questions. Then one can point to a given bullet # and question if it is not not clear. Nibbana is discussed at various levels (simple to deep) at:
Nibbana
By the way, Johnny_Lim has done a good job above in trying to express the main idea. But Nibbana is a deep concept. The last post in the above link discusses how the Buddha said Nibbana exists, but not in this world.