The end riff is exactly the same as the rest except it ends on C sooner, the parenthesis just indicate that that part is the same.
I'd suggest using the full bar for the F chord to create a nice baseline.
If you find the riff to difficult you cn leave out some of the bottom notes, I just think it sounds better this way.
I'm not going to write out all of the picking paterns, choose your own, I use mostly a pmia pattern (p = thumb, m = middle, i = index, a = ring)
If you're wondering what is going on when the Am chord is played (on dove ect.) the Am chord is played with a C on top and then an open B is played hammering on to C again.
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