I want to create a filter for the query string is this possible?

To at least answer the title of your question, the pre_get_posts filter may be useful. From the Codex:

This hook is called after the query variable object is created, but
before the actual query is run.

The pre_get_posts action gives developers access to the $query object
by reference (any changes you make to $query are made directly to the
original object – no return value is necessary).

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