My problem is the following. I'd like to have a script that is excecuted in Col(B) and checks the data of Col(A). If the value of Col(A) is < 0, than there should be a 0 in Col(B). If the value of Col(A) is not < 0, than there should be this value in Col(B).
I've tried it like
if (Col(A)[i] < 0){ Col(B)[i] = 0 } [else Col(B)[i]=Col(A)[i];]
Your expression would work if you looped over all rows in column A, but as written it will only work for whatever the current value of "i" is (and will fail if "i" does not exist or has a zero or negative value.
You can use the Ternary Operator to achieve what you want in either the Script Window or in Set Column Values:
col(B) = col(A) < 0 ? 0 : col(A)
In Set Column Values for column B you only need the right side: