Inside our Fork GitHub repository, how we can manage our changes with future releases done by the upstream, incase our files get modified by upstream

Question

I worked on many projects for building SPFx from scratch, and posting the code to GitHub, but I always own the SPFx, so I have full control on my code and future release..

Now I am working on modifying an SPFx that was developed by other contributors @ https://github.com/OfficeDev/microsoft-teams-emergency-operations-center .

Now I will do the following: -

1. Fork the repository
2. Apply our modifications which mainly include modifying the fields Labels and Description, mainly by modifying LocaleStrings.ts file.
3. Also, the current solution will create Assessment channel when a new incident item gets created. But in our case we need to create 5 additional channels and remove the Assessment channel. So, I will add the new methods to create the additional channels inside the following IncidentDetais.tsx file:-

everything is somehow easy to me from the coding part. But I am not sure how I can keep my Fork repository in sync with future updates from the upstream? let say in a future release done by the upstream they also modify the IncidentDetais.tsx by adding more channels, then how we can get those updates and at the same time keeps our modifications? Is there a way to do this? or we will need to manually merge our changes to the updated IncidentDetais.tsx file ?

Can anyone advice on this please? how the life cycle will be?

Thanks