So I would like to start studying Un Sospiro but I don't know if my level is high enough since I read on the website that the level is 8+.
Go for it the best motivation is wanting to play it.
Just be mindful of your time. Think like this: either it is " impossible to play" or it is "easy".
the difference is the time it takes to learn it. Be mindful of the time. Also practice enough slow.
You can also try together with this one Chopin OP 25 nr 1 as it is "arpeggio-related"
The most difficult part however is the page with the octaves (3rd page IIRC?)
Regards,
G