Calibration, Sensitivity Analysis, Numerical dispersion And Model Verification In An Ecological Model With 15 state variables

Question

I am a student assigned to a project on improving an ecological model. This model is 1-D model consisting of a dispersive-advective component and pelagic-reaction component which was developed in R. However, I have hit a roadblock on how to calibrate, run sensitivity analysis, numerical dispersion on it for model verification. I was given a report which stated that I had to manually fine-tune the parameters, however there is no code that shows how I can do it. I tried reading the book by Karline Stoetart: "A practical guide to Ecological modelling using R as a simulation platform", unfortunately, I am not able to implement the example in the calibration section because my problem involves 15 state parameters. I have tried reading papers but they all focus on automatic calibration schemes or give very vague descriptions about the manual calibration. Does anyone know how I can go about this please or give me tips or resources how to calibrate, run a sensitivity analysis, numerical dispersion and model verification on an ecological model with 15 state variables.

I am not able to even start model calibration.