My sisters phone

My sisters phone has been acting really weird most times when he wants to get on an app it kicks her out and her storage is full and she barely has any apps I have more apps,her phone turns off at random times then goes to this loading things then turns off and there’s times where her phone completely freezes and before she deleted Snapchat it wouldn’t load and it said something about it’s a camera app and there were other times it worked and she reset it and it still showed it’s a camera app and it also shuts down at random times. What should she do and is her phone fixable