I'm guessing 21f2 f3 x nutpunch and the dash 2 combos are giving you trouble? For the 21f2, it has to be a full dash after the f2. You actually have more time to do the dash than you think, and you're probably doing it too early. After the f2, just input a full towards dash, and hold down on
. Input the 3, and then do the nutpunch. You can get two f3's in, but it's better that you just stick with the easier combo for now.
Most people have trouble with the dash 2's combos. For now, you can substitute all 2's for 11 for your midscreen combos until you get the dash 2 down. The dash 2 is a quick dash motion, and then you immediately go to neutral (as in the joystick remains still) and input the 2. You can input another quick dash, go to neutral, and input the 2. It will take a little while to get used to because you'll want to hold down on towards, which inputs the f2, which is probably Cage's worst normal. Just keep practicing the dash 2, and stick with dash 11 for now.