WERE/WAS

[tanviet]

I am confused of use of "were", "was"

I think that
if the condition is unreal, "were" is used
if I were you, I would learn gmat

if the condition is possible, "was" is used

if the door was open, I would come in

is my thinking correct? pls help

[tanviet]

anyone know any website which said about this point of grammar, pls, advise. Thank you