You must know that you're battling Terra in Glitch Field, which means you have to use setup moves when fighting against Quagsire. You should know that in Glitch Field, physical and special moves are now determined by the move type. Special Attack stat and Special Defense stat are merged back to Special stat which is determined on which one is higher between Special Attack and Special Defense. Every Dark, Steel and Fairy type moves become Normal type moves. Dragon type moves deals neutral damage and Ghost type moves can't touch Psychic type Pokemon. Critical hit rate increases by one stage if attacker is faster than the target. Blizzard accuracy is at 90%. Psychic type moves gains 20% of power. You must have Synthetic Seed, too. It will be quite useful, I suppose. But before that, you must max the level depending on how many badges you have obtained.