Thanks for the tipp with Replicant.
Maybe in one or two weeks I will be test it.
But actually I think the big security problem is ME.
I fight against me to not install non-free software.... Today I install
chrome for one hour and removed it again... Is now my system broken? This
example shows me, that I have to learn so many things that a secure system is
actually not possible for me, because I am not clever enough to use it.
But at the end I will try very hard to work with Trisquel only with free
software.