Firstly, there is a lot of grammatical mistakes; secondly, I'm finding the amount of clauses a bit too much. How about:
Once during your turn (before your attack), if this Pokémon is on your Bench, this Pokémon may use one of its attacks. (You still need the necessary Energy to use each attack.) If you do, discard this Pokémon and all cards attached to it (this does not count as a Knock Out). (Your turn does not end if this Pokémon attacks in this way.)
I don't think you need the second bracketed clause you put in, so I took it out.