The game allows you to get tamer points to unlock skills for various things, for your training point, there's things to gain more points to the training, allow you to slow the arrow down, and increase the likelihood of getting bigger green areas during training, I play on my tablet myself, some of the items are harder to see than others but it's not impossible unless you are playing it in a small window, but as far as training goes, it's not very important to be perfect with it, especially when you get around ultimate level digimon, just increase their levels and possibly equip some gear to them, then tackle the card digimon, you'll get a lot of S capsules for training, the max I've seen is 500 points so it's not very high.
But as for the battling system, it's okay, after all I don't expect a rookie lvl 100 beating an ultimate or higher, but I do expect it to win battles in it's own evolution area maybe champions if the stats are high enough, but I do like that even at max lvl and a mega you can still be defeated by certain digimon, if the starting grind is too much as it does get dull after a bit, try to focus on the card digimon to evolve and explore new areas, or try to unlock the challenge area, it'll also add new characters to find around the world as you beat the challenges.