Catia v5 r21 problem

Hello everyone, please i require assistance with CATIA v5r21 . so when i try to use the app it functions weirdly as if its bugged for instance when i delete or undo a line it reappears but disappears if i select a new command also sometimes the lines and circles colors change entirely tried reinstalling many many times didnt work my friend installed the same file faced no issues my pc is 64 bits does that affect it