Gyarados is weak to [Electric] and [Rock] types, while being resistant to Fire, Water, Fighting, Ground, Bug and Steel types.
For the details of the update, tap the link below.
Some of Pokemon got their moves changed or removed | PokemonGo
What is DPS and EPS in Pokemon Go?
Best Pokemon to beat Dragonite
Advanced Tips for Catching Pokemon
Best Pokemon to beat Muk
Best Pokemon to beat Machamp
How to use 'Poke Assistant' for team building