Respuesta a "Why isn't my phone turning on"Well, I’m not an expert at phone repairs, but your battery might just be bad. Usually when something doesn’t turn on and you’re not sure what’s wrong, you should first look for bent pins inside the charge port and try a new battery. Since the chargimg symbol appeared, the charge port seems to be fine. Be careful when handling batteries though, they can explode or catch on fire very easily. A new battery for your phone would cost 19.99$ here on ifixit.
Respuesta a "Replacing battery it will invalidate the waterproof?"Yes, it will. Even if you replace the adhesive, there is no guarantee your phone will be waterproof again. Taking off the back cover will also void any warranty you may have on your phone.