Each world has several levels, though you can only select them by roulette for whatever reason. Level designs are variable, the amount of Bombermen you fight is variable (though never more than three as far as I got). Basic Bomberman fighting.
Completing a stage gives you experience points, and such-and-such amount of experience points will get you a level up. Levelling up gives you points to spend on attributes - bombs, blast radius, speed, and time. I... think this determines your maximum capacity of those items? Like, you can collect Bomb Ups, but they'll never surpass 3 until you level up? Didn't get a chance to properly investigate. Given how tight the time limit is, I imagine you need to level up the time option before attempting some of the later levels in the game.

Each level has a percentage, and it all adds up to a world percentage. Levels need completed multiple times (or needs all treasure chests collected, I can't remember) to get 100%, and when the world percentage is 100%, you can move on to the 100 Man Battle!

Sadly, the goal in the 100 Man Battle isn't to defeat all one hundred opponents... it's just to survive long enough fot the Exit Gate to appear. There's only a small scattering of soft blocks and some of these levels ditch the hard block grid, meaning you've got wide open spaces to walk around.
Since there's so few soft blocks, there's very few items, and barely any of the opponents have a blast radius longer than 2 tiles. It's hard to actively kill any opponents, but it's easy to walk into explosions since the screen is so busy. In these stages diamond panels randomly appear on the map - collecting these gets you money, as far as I'm aware.
After the 100 Man Battle, you move onto the next world and the routine repeats.

While I'm talking about the actual battling, it is slow as hell. Even when it's just one on one, it's slow! Even after collecting four or five Speed Ups, IT'S STILL SLOOOOOW.
I haven't experienced iOS touchscreen controls first hand, but I can't imagine they're terribly precise, so taking it slow is probably a sacrifice for compatibility... but jeez, you really need that two minute time limit for most of the fights, it takes so long to reach them.

The treasure chest panels contain random things, either money, experience points or Bomberman panels. I never collected all six panels, but I assume these either unlock new costumes or new partners. The costumes include stuff like wedding gowns, animal outfits, cloaks and other guff. They're all unique sprite sheets, so you can't mix and match them, sadly.
Speaking of partners, after a regular stage you're given the option of returning to the map, levelling up your stats, or recruiting your opponent. If recruited, they'll appear on the bottom menu bar during regular stages and throw items onto the playing field. In the 100 Man Battle, they'll walk around (as white silhouettes) and try to attack enemies for you. I'm guessing this is how it'd work in human multi-player, but I obviously can't confirm.

Money can be taken to a shop and spent on items... I think? There's Bomb Ups, Speed Ups, Fire Ups, Kick Shoes, and one item that wasn't unlocked yet. I seem to recall starting every match with only the bare minimum equipment, so either I was doing something wrong or you're spending money just to find more items in each stage. I don't know. See, this is why I was looking to get the help page translated - I don't understand half the stuff that goes on!

Looking at the game files, there's at least 12 worlds and over a hundred arenas, so there's no shortage of battles... but what's the point if none of it is any fun? If anything, I respect how they're trying something other than ye olde "blow up all the Balloms!" gameplay, and all the stat-building repetitive-tedium nonsense to cater it to mobile gaming is an... intriguing addition. But, yikes, is it not fun. It's slow, the AI is underwhelming, the gameplay is clunky, and your only real reward appears to be different backdrops and more opportunities for Windy to wobble at you.