Thanks for the quick replies!
And how I know that nobody can track my bitcoins back?
Any other way then the "simple taint check"?
"Simple taint check" = taint analysis of the wallet which received the bitcoins through an bitcoin mixer and then simply press Strg+F and type my origin wallet in the mask. And if there is no listing of my origin wallet in this taint analysis I'm "anonymous" (if my VPN Provider & the mixing service both not logging)

So you mean for example if I buy the bitcoins with my bank account and then send it through an bitcoin mixer to a completely new address and then withdraw this mixed coins to my wife's bank account. It is possible that somebody could track the money from my wife's bank account back to it's origin (my bank account)? I know it's not the best example but hope you understand what I mean.

Hello bitcointalk,
is it possible to stay (online) 100% anonymous with bitcoin?
I heard about bitcoin mixers but how can I see that it is really impossible for everyone to track the coins?
Read a couple things about the blockchain taint analysis but is there no other way to get the original origin?
Btw. I'm really sorry for my bad english it's not my mother tongue.