please remove all sublists

It could help to take a type-driven approach here. As in, you want to remove all occurrences of some element from a list of list of elements.

This is, “given an a and a list of list of a's ([[a]]) return a list of list of a‘s ([[a]]):

removeAll :: Eq a => a -> [[a]] -> [[a]]
removeAll v (list:listOfLists) = ???

We’re removing all v from each list in the list (list:listOfLists). Another way of saying this is “for each list in our listOfLists filter out v.

So, we want to perform the same action (filter) for-each value in a list. In Haskell, this translates to mapping the filter action over every list in the listOfLists.

removeAll :: Eq a => a -> [[a]] -> [[a]]
removeAll v xs = map (filter (/= v)) xs

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