Welcome to Osu!
I'm not a mod, but comments are better than no comments. =D
It looks really good, especially for your first beatmap. I think the BPM is right on as well. You have a good idea of where to place beats for the most part. While the rhythms are really simple and straightforward, you kept things interesting with creative beat placement... However, at 24:68, 44:47, 50:51 and 3:27:11, the beats are a little far, it's kinda hard for us mouse users.
This is a really long song by Osu! standards, so I think some breaks are necessary. I know it's hard to erase some of the mapping you've done, but it really has to be done. Those spots where it looked like you were filling space with spinners, like 2:38:00 would be ideal spots to place breaks. You decide though. =D
The beatspacing looks good, except at 2:49:16, the yellow 6 is kinda close to the others, and in the similar repeated pattern.
It's a good beatmap, and I wonder what you'd be capable of with a song that you're familiar with. =D