First, you'll improve as you improve. don't focus on how fast or slow you're improving compared to anyone else or else you'll potentially be stuck in misery wondering why people with the same hours as you are higher ranked.
Second, you as a 1.2M shouldn't even be touching anything about 3* other than for fun. You may have some grasp of rhythm, true, but that doesn't translate to having the coordination, muscle memory, or speed to play those difficulties to any reasonable degree of competency. You should be at the high 1* to at most mid-2* range and work on keeping high acc there first (at least 95%, preferably with an FC but that's not expressly required). If that proves to be too easy to do, then increase it by about .3-.4* increments until you start having trouble keeping combo, and that will be where you need to start working on improvements.