Adjust existing R-Code to loop over existing model calculation and plot on facet grid

I have an existing R-Code which subsets a data frame from a larger data frame, then runs two models (GAM and GAMM), shows the result and plots them. I need somebody who writes a loop around that code which 1) gets 1 to 5 subsets of the whole data frame based on a factor in the data frame 2) calculates the models for 1 to 5 and and 3) plots the models 1 to 5 "nicely" within one facet grid with same x- and y-axis. Please see existing R-Code attached. In a perfect world I would like to adjust the e code later on myself for other tasks of the same kind.