There is no legitimate way to obtain unlimited Primogems in Genshin Impact. Primogems are the game's premium currency, and they can be earned through various in-game activities, quests, and events. MiHoYo periodically offers Primogems as rewards, but they are limited and should be earned through legitimate means. Any attempts to cheat or use hacks to acquire unlimited Primogems are against the game's rules and can result in a ban.