Are whey protein isolate powders safe to drink if I drink lots of water with it? 1.4 liters - 2 liters a day of water, 1 protein shake after gym.

Probably. Protein shakes can be problematic for people with kidney problems or who don't stay well hydrated. So long as your urine is light in color or clear, and you tolerate the drink (no gut symptoms of allergy or intolerance), it's unlikely to harm you. Be careful of calorie content in your shake, though; some are surprisingly high in unnecessary sugars.