Filter import date to latest date on that date

I think this could work

Find max import date

then check to see if that max date = import date

of yes then filter that

i know what i want ti achieve but cant put it in a power query formula

It picks up the first value of table through Table.FirstValue which is the date in your case.

Corresponding to this date, it finds the last Sunday which is 23-Jul for 26-Jul date. Then it will generate Monday (17-Jul) to Sunday (23-Jul) list. 

Filter will select only those rows where Import date lies in this list of dates.