Add whatever filtering on values you want

(* In DataxzStein, x is column 1 and z is column 2 *)
DataxzSteinSubset = 
 Select[DataxzStein, Between[#[[1]], {-0.32, 0.32}] && Between[#[[2]], {-0.22, 0.22}] &] 

MinMax /@ Transpose@DataxzSteinSubset
(* {{-0.315, 0.315}, {-0.215, 0.215}, {0.447852, 0.889891}} *)

Use DataxzSteinSubset to fit.

Hi Rohit,

Thank you so much for your time and consideration. But let's say I want to extract a specific range of data from my column data points for fitting; how to do that?

Sorry for the silly question. For a beginner, I am struggling to learn. It would be helpful if you answer this.

Regards, Soumyaranjan