Removing text after character or between characters

It looks like you are mixing up DAX, Power Query and Excel.

Also your requirements are not very clear.

Just a wild shot:

In the Query Editor, I created a Parameter SearchValues:

And I created the following query that adds a column with found keywords:

let
    Source = Table1,
    #"Added Custom" = Table.AddColumn(Source, "FoundKeyWords", (This) => Text.Combine(List.Select(Text.Split(SearchValues,","),each Text.Contains(This[Page],_)),", "))
in
    #"Added Custom"

With adjusted example data, the result looks like:

If this is not what you are looking for, then it might still help you to reformulate your requirements.