Hi, you could try the combination of three Gauss function like below
Root of Mean Square Error (RMSE): 2.2458311950253
Sum of Squared Residual: 711.169843673375
Correlation Coef. (R): 0.995653625154367
R-Square: 0.991326141283032
Adjusted R-Square: 0.991200433185684
Determination Coef. (DC): 0.991326141283033
Chi-Square: 6.21518727937255
F-Statistic: 1663.53905384453
Parameter Best Estimate
---------- -------------
y0 3.38248250695097
a1 -3.40352177296373
w1 -0.0629005260678393
xc1 0.633232228609099
a2 5.12621647096813
w2 0.218653477675725
xc2 0.601814960692917
a3 3.60981050580609
w3 0.0527170754308885
xc3 0.565564482020339