Sometimes you can find answers only by looking for synonyms. When learning a language, avoid your mother language as much as possible.
circumvent:
avoid, prevent, avert, escape, bypass.
overcome:
surpass, pass, get over, break, conquer.
As you can see, circumvet is about avoiding a situation, escaping from it. Overcome, on the other hand, is about dealing with it and solving the problem, or getting over a situation.
Tell me wether it's clear. I can provide some examples :)