How can I force all the letters go left to right including the characters from right-to-left languages in all buffers? Currently it displays the lines with right-to-left characters bidirectionally.
Bidi reordering is controlled by the buffer-local variable
bidi-paragraph-direction. You make it default to L2R by adding the following incantation to your init file:
(setq-default bidi-paragraph-direction 'left-to-right)
(There is also
bidi-display-reordering, but that can lead to crashes and should not be changed unless you're debugging Emacs itself.)