I have tried simplify some expressions to DNF and CNF but I'm stuck in one step and I can't find some rule or law what can I apply on it. I used Wolfram and found that my expression is not in DNF/CNF yet.
On DNF I'm stuck here: 
but the DNF is:
On CNF I'm stuck here:
but the CNF from calculators is:
Please can someone help me with some tip, rule or law what can by applied to solve the problem? I spent hours with it but with no progress.
Try:
Adjacency
$PQ+PQ'=P$
and
Absorption
$P+PQ=P$
Applied to your first expression:
$$C'D'+CD+B'D'+BD \overset{Adjacency \ x \ 2}{=}$$
$$BC'D'+B'C'D'+CD+B'D'+BCD+BC'D \overset{Absorption \ x \ 2}{=}$$
$$BC'D'+CD+B'D'+BC'D \overset{Adjacency}{=}$$
$$BC'+CD+B'D'$$