What should be the workflow for template repository and private repository?

I have limited knowledge, so please bear with me if my question sounds silly.

I am describing here what I am trying to achieve.

I want to create a public template repository (a static site template with jamstack) that others can use.

I also want to use the same template to build my site including my data. So I want to keep that in a private repository.

In the future, I would like to (possibly) update the public template and then need to receive the changes in my private repository.

I have found a solution that seems feasible but I can’t understand how to handle the marge conflict in the future when I fetch changes from the public template repository and merge those changes in the private repository. In the private repository, I will have some changes in the same files. For example in public template file A has some placeholder text. But in the private repository in file A, I will replace the placeholder text with my actual text.

Also, I will have some example files in public which I will delete in private.

Thanks in advance for your help.