I finished going through N4 recently and am reviewing everything I learned. I feel like ma is more difficult to master than everything else. The sound changes all seem random to me. Any advice?
For some of them there are rules that might help and that aren’t specific to this grammar point.
For example, the small っ normally doesn’t occur before vowels, so in something like 真っ青 or 真っ赤 we can at least expect that it’s not the ”normal” reading.
It also generally doesn’t appear before m or n, and ん is used instead. This also applies to other words where the romanization would have a double n or m.
It also doesn’t normally appear before h or before voiced consonants, so e.g. in 真っ平 that only leaves まっぴら as the only option.
But in some cases it’s just unknown where the change comes from. E.g. the extra S in 真っ青 (まっさお)、真っ新 (まっさら) can also show up in other words even without a small っ like 春雨 (はるさめ) or 荒稲 (あらしね) but I don’t think anyone knows where it comes from.
You can also just learn the words individually of which there isn’t many tbh. That’s the easier way