Red: You must fix this.
Blue: You'd better do sth with this imo.
Green: Just suggestions.
[General]
BGwww.jpg is 800*601= =... make it 800*600.
the hitsounds is a bit loud imo.
try to use more sliders in your diff (Easy/Hard/Insane) to make different patterns, will make your map more fun.
try not to use grey as a combo color because it's similar to the failed color (during MP)
[Easy]
00:04:255 (5) - new combo
00:08:992 (1,) - remove new combo and use a slider instead since this is 3/2.
00:21:623 (2,1,2) - spacing?
00:34:255 (5,6,1) - suggest use a repeated slider instead.
00:49:058 (2,3,4,5,6,7) - use sliders instead those 1/2s.
[Nivalis' Normal]
it's obviously a Normal+, maybe rename it...and why not map the full song?
00:09:979 (6) - too loud. if you want to use those finish, add a timing section before it to lower the volume and another one after it to turn volume back.
00:18:071 (4) - nazi. 1 grid left.
00:36:623 (3,4) - repeat (3) once more and make (4) a circle= =?
[Hard]
HP Drain Rate-1 and Overall difficulty-1.
00:04:255 (7,1) - switch new combo.
00:15:308 (7) - clap at the 2nd repeat.
00:49:058 (3,6,8) - whistle.
01:41:163 (10,11) - nazi. 1 grid right.
01:46:886 (4) - new combo.
use more sliders instead the non-stop 1/2 circles= =
[Insane]
Overall-1
00:07:018 (8) - sounds strange. why sudden change the hitsounds.
00:24:189 (6,7) - spacing.
00:35:044 (1) - remove new combo.
00:42:150 (9) - new combo.
01:34:255 (1,2,3,4,5,6) - spacing. (2-3 =!= 5-6)