Fitting the curve problem

I try to fit an s-shape curve with the function that I define. Actually I get a not-so-bad fitting by setting a more appropriate boundary and starting point. One remaining question is that although the fit is better, the parameters' range is still big. Anyone has any advice for this? Attached file is the data file for Ch4.

Final_time=10;
recordLength=size(Ch4);
recordLength=recordLength(1);
Time=[linspace(0,Final_time*1000,recordLength)]';
Ch4_mV=Ch4.*1000;
[pks,locs]=findpeaks(Ch4_mV,'MinPeakProminence',30);
for j=3
   duration_fit=Time(locs(j)-6:locs(j)+10);
   y_duration_fit=Ch4_mV(locs(j)-6:locs(j)+10);
   FitFunction=@(a,b,A,B,F,e,x)F.*(b.*A-(x-a).*B)./((x-a).^2+b^2)+e;
   options=fitoptions('Method','NonlinearLeastSquares','Upper',[Time(locs(j)+50) Time(8)-Time(1) 1 1 pks(j)+10 0],'Lower',[Time(locs(j)-50) 0 -1 -1 pks(j)-10 -15],'StartPoint',[Time(locs(j)),1,1,Time(locs(j)+5)-Time(locs(j)-2),pks(j),1]); 
   [fitcurve,gof]=fit(duration_fit,y_duration_fit,FitFunction,options)
   plot(fitcurve,duration_fit,y_duration_fit);
end

[Stephen23]

Context: https://www.mathworks.com/matlabcentral/answers/1662235-fitting-the-curve-problem

[KSSV]

You can try polyfit.

[Yumeng Yin]

Thanks, but I have to use this model to do the fit.

[Sam Chak]

Looks like the Stribeck friction model. No harm trying to fit with the suggested model, but you need to shift the center to approximately .

https://www.mathworks.com/help/physmod/simscape/ref/translationalfriction.html