Help I'm Stuck

I’ve just beat the 7th gym and had to fight Mewtwo but I lost to it and know I don’t know what to do. Could you guys please help me?

You mean Mew? Mewtwo isn’t till postgame. Also if all else fails you can always load a backup and try again

It was a Mewtwo I fought.

are you on a randomizer or something? cuz otherwise that isn’t possible, unless it was a trainer’s mon or somethin

It was a Cultist Leader or something.

I re-loaded the game and got sent back to a place before it happend.

ah i forgot reukra has shadow mewtwo. So it works now?

I need to win the Gym badge again.