does anybody skip some part of the piece because it was boring?

[robson]

I mean do we have to learn i play the whole written score if it's not good?
Many time some parts especially a coda or some other parts
are not so good as a main theme so I skip it and play improvisation instead.
Kinda like a jazzy way 

[jayeckz]

You technically don't have to do anything.  In my opinion, do what you want, however, I wouldn't recommend deviating from a written score and playing an improvisation in a competition or an audition.

Why do you ask this?

[49410enrique]

hmm prolly works, heck even a good idea if you're good with a concerto cadenza, those are improvisatory in nature (unless score explicitly states play as written or if it is part of the score and only an 'implied' cadenzy, i e cadenza like passage'.

for example

1.Ashkenarzy(Haitink) 2.Hamelin 3.Argerich 4.Andsnes(Berglund) 5.Ouset 6.Volodos 7.Gavrilov(Muti) 8.Katsaris 9.Kapell(MacMillan) 10.Kissin 11.Gilelis 12.Cliburn(Kondrashin) 13.Grinberg　14.F.Kempf 15.Kocsis　16.shelly 17.Janis 18.Zilberstein 19.Vasary 20.Trpceski 21.Nanasakov(Virtual pianist) 22.Nikolsky 23.Hough


other than that i'd stick to what the composer wanted, unless you just want to play around for your own enjoyment, that's different alltogether. i'd at least then learn it well as written than do whatever in your practice.