Should I use Optimum Nutrition 100% Gold Standard Whey and Casein along with Scivation Xtend if I wanna lose..?

Diet sounds good. However, you cannot simultaneously build considerable muscle mass and lose lots of fat at the same time. If you want to build muscle mass, lift heavy weights, 1 different body part a day 5 days a week with 3 - 5 different exercises for that one body part you're doing that day and with 3 sets of 8 - 10 reps for that one exercise. To lose fat, you just need to burn calories through eating less than normal or through exercise. Whey and casein and extend should be used mainly if you want to build muscle. You need protein to build muscle and that's what they're for. Lastly whey and casein are just protein, you can get protein from lean meats, but whey and casein are special because they repair damaged muscles when you lift weights faster.