so with out using the cheat in the new update how many more times u need to hit the bag?
It depends on how much leftover experience you have, the better you do at the sandbag minigame, the more experience you get. If you always strike with an almost perfect force, the timer will increase slightly, so theorically you might need to play it only once if you're really good at it.
In future once the battle system is completed, skipping battles through the use of FPs will grant you the same experience as winning the battle, so up to that point the required experience to progress with the story will be much less. The game is balanced with the battle experience in mind, so unfortunately right now you have to grind a little bit to make up for the missing experience.