Hi,
go to Control Center > Hardware > Sound and take out the tick in "Enable window and button sounds", or you can mute it!:
As far as the kernel goes, if you have your software sources set correctly, you won't have to worry about kernel installation as it will do it automatically on regular updates, don't mess with single kernel packages if you don't know what you are doing or you may well bork your system!.
See the update guide for more info about software settings:
What version of Ubuntu Mate are you using?.