Alright, so first of all, watch some tutorials on getting to know mapping better, (pishis vids are amazing), play around with the editor a bit, learn all the tabs and all the fancy stuff you can do with the editor, now then.
If you're looking to make a map thats around 2-4 stars, you should use grid snapping, time your bpm correctly, and try to make patterns, of course use sliders. One thing I noticed was the constant use of spinners, I think that spinners should really used in an intro / outro of a song, or right before a break starts. And then the difficulty set up, or press F4. The Approach Rate (AR) is too low, usually it would be somewhere between 7-8 for a 3* map. Oh and the circle size is too small, whatever you do don't make it bigger than 5, but if you can manage the spacing correctly then it should be no problem.
Timing on the first part is solid, although it seemed you were really having trouble to map the main chorus, since this song isn't really fast like DDU-DU DDU-DU where it has a solo aswell, try to use both vocals and the instruments whenever the vocals aren't playing. If I were to do it, I would only use little of the vocals, probably only when the lyrics are continuous.
Oh I forgot, you should probably look at other mappers styles like Sotarks, pishi, monstrata etc.
I hope this helps!