How the battle in high rank works?

I have join in rank 50 recently for first time but i suffered a lot to became rank 50 and during the time i reached it i saw a lot of moves that i didnt understand, as every time i tried to use a ultimate card, sometimes had a time to dodge it, but other times not and i do the same moves to do it, after a combo i use the main ability and instant use the ultimate card and the same thing occurs when enemy does the same... i want to know how it works or how to know when it works to dont lose that card... ty ^^