I thought ér 二 was ‘two’ can you explain?
The two are actually quite common. er, actually is mostly used for counting, but it seems that in practically 90% of situations people are actually using liang. Needless to say, when in doubt fall back to liang (unless you are counting from 1-10 or something like this).
I live in China, and consistently get it wrong, and have realized that it really depends on the person, even a new Chinese tutor I just hired who understands grammar and can explain most things quite well, can’t seem to explain the subtle difference to me.
Don’t give up, keep working on.