Re: problem is real masured & simulation different in CST
S-parameter values depend on the chosen reference impedance. You need to be careful what impedance they refer to: 50 Ohm fixed or the line impedance seen at the port ("generalized s-parameters")
I am not a CST user, so I don't know where you can find input impedance in the results. In other tools, it is often called "Zin" or something like that. Verify that the tools gives the value with 50 Ohm termination on the other end, so that you can directly compare to measured. Or calculate it yourself from S11 using the 50 Ohm S-params.
One common reason for difference between EM solver results is the user himself, and his solver settings.
What I do see in your screenshot is a solver warning that simulation stopped before steady state was reached. Check your settings for time steps.