Understanding Prefixes: Un, Dis, Im, Mis

A prefix is suffix which is always placed in the beginning of the root of a word to change its meaning and may not be written separately (with space). Particularly in the linguistics study, a prefix is also called preformative.  For example, re + verb means doing something again, back as in return, repeat or refurbish.
These are four prefix which is something very confusing because they all have negative meaning. I am interested to explain this kind of prefix that I found a question about this in a TOEFL test.
un-
The prefix un means not, reverse action, deprive of, release from. For example, unable or unfair.
mis-
The prefix mis means wrong. For example, mistake or misunderstand.
dis-
The prefix dis also means not and opposite of. For example, disconnect.
im-
The prefix im can also mean not and opposite of. For example, impossible.