Not if you stay and study it long enough. Eventually all of the skills will be learned. Karate evolved out of kung fu.
Ninjas don't use karate or Kung fu. They use ninjutsu.
No, they are not the same. Kung fu originated in China. Some aspects of kung fu have been incorporated into various styles of taekwondo through the Okinawa karate styles.
Karate came from Okinawa, which is now a part of Japan. Kung Fu is from China.
It depends on what you mean by mix. Karate already incorporates aspects of kung fu.
Kung Fu
You should check out the Shidokan of Canada school in Guelph. They teach traditional Okinawan karate, which has its roots in White Crane style Kung Fu.
In general techniques, they are very similar. Karate is based partially on kung fu. To say that they teach different things would be incorrect. Both are martial arts that were taught to soldiers and fighters.
Karate
Kung fu comes from China. Shaolin monks teach real kung fu there.
Kung fu can to China from India. Bodhidharma a Buddhist monk traveled there. Kung fu was taken to the Ryukyu Islands and became Karate.
Kung fu