Power query support for tricky question

Dear community

i have a tricky question

i have a table "cross-Domain extract file" and  3 coloumns stated below

1)  “ClientSectorDesc” 

2)   "Sector as per Account list"

3)   "Account Name_Lookup"

In the table "cross-Domain extract file"

Filter Banking &Capital market in coloumn “ClientSectorDesc”  &

Select Null in “Sector as per Account list” column - Replace Null with BCM

and also With same filters on Replace null in  coloumn“Account Name_Lookup” with Others.

after the changes made, unfilter everything (like we do in excel)

how do i achieve this in power query as i wasn't sucessfull using  filter, find and replace steps in query editor