As long as you did not have your BitCoin on a bitcoin-stockexchange, during the split fork, you now have both BitCoin cash and Bitcoin core, right?
Yes.
As long as you created your address on BitAddress, and then memorized the address in your head, on a paper or in cold storage, you now have both types of BitCoin, right?
Yes.
Is there some other scenario in which you now only have one BitCoin, except for those who had their BitCoin on an exchange during the split fork?
If you acquired your bitcoin after the fork, or if you no longer have access to the private key where the coins were secured at the time of the fork after having moved one type to a new address.
If you have two BitCoins, how do you go about selling your BitCoins now?
Bitcoins? The same way as before.
And how do you know if you are selling Bitcoin Core or Bitcoin Cash?
You choose which one you want to transfer.
This is confusing to me. So If you send your BitCoin, from your old private adress, from bitadress, to an exchange that supports both types of BitCoin, will you then have two bitcoins showing up on that exchange?
Assuming that this exchange supports both bitcoin and bitcoin cash I mean.
No.
If you send 1 Bitcoin, then you will only have 1 Bitcoin showing up. You will still have access to 1 Bitcoin Cash at the original address (since you didn't send that anywhere yet).
If you want 1 Bitcoin Cash to show up, then you'll need to use a Bitcoin Cash wallet and send Bitcoin Cash.
If you had one Bitcoin before the split, will you then have one Bitcoin on that exchange and one token called Bitcoin Cash? So they will show up as two coins there?
Only if you send both (using two separate transactions, one for each type of coin).
Or what do you mean that you did not double your amount of bitcoins? I understand that you have the same amount of Bitcoins as before. But you also have as many tokens of Bitcoin cash as you have Bitcoins, after the split. So in effect you doubled your bitcoin even though it is not the same kind of Bitcoin, or is this wrong?
Bitcoin is not Bitcoin Cash. It's confusing because they chose a confusing name. Imagine if they called the fork Niocib instead. You'd have 1 Bitcoin and 1 Niocib, not 2 Bitcoin. The same is true here. You have 1 Bitcoin and 1 Bitcoin Cash, NOT 2 Bitcoin.
I still don't understand if my total worth is now about 4900 per Bitcoin?
No. It is 4200 per
Bitcoin.
However, you also have received (for free) an equivalent amount of new asset called "Bitcoin Cash". Your total worth is 700 per Bitcoin Cash.
Because for every bitcoin I can also claim one Bitcoin cash now, or am I right?
Correct. For every Bitcoin, you also have an equivalent quantity of Bitcoin Cash.
So my total value should be about 4200+700=4900
Correct. Your total value is approximately 4200 for every Bitcoin you own and approximately 700 for every Bitcoin Cash you own. I assume you have other value as well (car? house? clothing? food? etc).