When a file (nam) isn't executable you can do : chmod +x nam
! No need to change anything with the /usr/local/bin/ folder !
You should be able to fix /usr/local/bin/ with :
1) su <password> 2) chmod 0755 /usr/local/bin/
I can't login as root I give authentication error
It is never required ( or recommended ) to log in as root.
"su" in a terminal will do.