How to return previous date based on a criteria with expanding data

https://preview.redd.it/e2bkheeonhfg1.png?width=379&format=png&auto=webp&s=d05e6d547029b535737bb102fb521d494a9cc03a

I have this data. I want the value in B6 to be the date from C4 follow its criteria from column A. Then the date in B10 to be the date from C6. The data will be expanded daily. Hope anyone can help me.

Thanks.. :)