Answer to "An issue with the RAM"Might be you are running lots of applications at the same time, or you installed some unwanted applications which should not be there in your computer so you have to cleanup your computer and remove all the bad and unwanted stuff from your computer.
Answer to "Why does my Lenovo Yoga 3 keep freezing?"Might be you installed lots of unwanted application which should not be there. Or you are running lots of files at the same time. So please do one thing restart the computer then you should clean your computer.
Answer to "suddenly the phone restarted and sim slot1 is not working"Remove the sim than restart the phone and try to put the different sim then it will gonna be work.