Professional mania players have at least 500 hours, i think it translates to about 20 days of playtime. Most people say play more, but there are some specific things you need to practice for different people.
If you are getting less than 90% acc on each map, you need to practice accuracy,
where as if you watch a replay of yourself and you're missing all the long notes you need to do more LN practice
Personally i've given up on 4k and am playing 7k, started today