Thank you all very much. I appreciate it.

I see the advantage of a good mixer now.

But back to the other method:
I do not understand, why privacy (cutting the trace) is better when I make A) instead of B).

A) I use Bisq to switch my BTC into Monero and switch back to BTC (with a different amount).
B) I use Bisq to switch my BTC into ETH and switch back to BTC (with a different amount).

I know, that Monero does not provide a history of the past transactions, but ETH does.
But why is this relevant in the case of switching BTC into another coin and switch back to cut the trace?
The trace on the ETH, if I would use ETH, is not from me. So the past transactions of this ETHs would be useless, if somebody would try to follow my past transactions. What am I missing?

Would be thankful for an answer. Thank you.