Funny thing about language: It actually gets harder to learn once you stop being a learning sponge around the age of six (at least when it comes to speaking it). Actually learning any language is hard work, and does require focus; I don't think any language can be quantifiably called the "hardest language to learn EVAR!!!!" due to the nuances in each individual language.
As far as the I before E rule, remember that is goes "I before E, except after, or when it sounds like A, as in 'neighbor' and 'weigh.'" In this rule, "weight" still fits. Exceptions include, but are not limited to "height," "weird," and "foreign." "Being" might seem to break this rule, but not when you think about how you conjugate the verb "to be."