If Biotest protein shakes are anything like the normal whey protein shakes as far as decomposing over time, then no. Mix and drink. I dont recall reading much about it, but that would be my first guess. Someone can glad correctly me but I believe thats right.
Eat more food and less protein shakes. You need to be eating fruits, vegetables, leans meats, etc and not concern yourself so much with the number of protein shakes. If you're eating more powder than solid food, there's something wrong. I drink one or two shakes a day, 40 g of protein each. Protein shakes ought to be a good addition to a healthy diet, not a replacement.
Do a search and this would be answered easy enough. Yes its fine to mix your shake a few hour prior. It wont degrad just try and keep it cool. If it does degrade in a few hours it wil be minimal. If it is simply easier for you and the only way then mix ahead. If you can add water later then just have the powder in a bottlew and add the water when needed.
Shakes are a great supplement to a solid whole food diet. Add them as needed to meet your needs. No you cant have to many really. But yes to much of anything will make you Fat.