Not sure if this is correct place to post this?

I just fresh installed debian stable with kde
than installed firefox and thunderbird than i add links to desktop
when i tell firefox to use its icon all exe's change to firefoxes icon
when i set up thunderbird icon the change to thunderbirds icon
and back and forth
ive deleted ect/tmp/cache-username$
and that was not a fix

any help would be nice

How/where are you trying to change the executable icon?
Usually a *.desktop file for each application will have it's own icon.

ok i downloaded firefox and thunderbird than placed folders into home directory as instructed
than i made icons as suggested by firefox and thunderbird when finished they were the same
and all exe's on system now have same icon for them the thunderbird icon
so i changed firefoxes back to it now everything has firefoxes icon and back and forth with each change

Which instructions are you using here? Usually applications are installed from your package manager - it sounds like you are retrieving them from somewhere else...