Drop-down list based on another cell value

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Simple question maybe, help pls.
Column A (not unique values), Column B (unique values).

In F and G columns need dropdown list, based on A and B columns values. If category 1 (1st drop-down) then can choose one from all values for that category (drop-down 2).

Looks simple, but in column A values are not unique... And it not comfortably
And I need to avoid any helper columns.