How to apply GEE and how to use it for critical mass

sorry I am completely new to the forum and as well to using GEE and SPSS so I hope my question is not to confusing.
My dependent variable is the firm performance and I have several controlling variables. First of all I am not sure how to set up my independent variable. I would like to find out whether there is a critical mass of women influencing the performance. The hypothesis is, that the performance increases when there are at least three women. However, I need to test whether this hypothesis is true. Therefore, I am looking at 8 years of panel data. That is why I was told to use the GEE method.

Hypothesis 1a: There is no relationship between one woman director and the firm performance.
Hypothesis 1b: There is no relationship between two women directors and the firm performance.
Hypothesis 1c: There is a positive relationship between the critical mass of women directors (at least three women) and the firm performance.
I was talking to various professors and supervisors and they all gave me contradicting opinions on how to set up the independent variable, therefore I ask again here. I hope you can help me.

The second question relates to conducting a GEE analysis in SPSS with this data. I have never used this method. I know there are several tests I have to run for an OLS (normal distribution, VIF score, etc.) but I have no idea what the important tests are in the GEE method in order to make sure all assumptions hold and the model is overall making sense.

It would be amazing if some of you could help me!