Regarding your remarks:
"  I ask you a justification of the results of the third column that comes from a real experience and
reproducible that helps a person to understand clearly and to fix in the mind the concepts it represents.

P | Q | if P then Q
------------------------ 
V | V |     V       
V | F |     F       
F | V |     V       
F | F |     V 

I ask this because in my opinion, "if P then Q" and "only if Q then P" are equivalent is, but I think hide critical aspects
I want to discuss with you."

OK, Fabrizio, here is an ordinary example:

• Suppose someone sincerely asserts S, namely ‘If the lit match is dropped into the pile of oily rags, the pile will ignite’.

• Consider the corresponding material conditional (MC): ‘the lit match is dropped… → the pile will ignite’.

• Clearly, if S were true, we would expect the pile to ignite when the lit match is dropped into it; so the 1st line of the truth table for MC is uncontroversial.

• Clearly, if we dropped the lit match and the pile did not ignite, we would regard S as false; so the 2nd line of the truth table for MC is uncontroversial.

• Some people balk at the 3rd and 4th lines.

• However, if we did not drop the lit match, but the pile ignited anyway due to spontaneous combustion, this would still be compatible with S’s being true. So line 3 is vindicated.

• Likewise, if we did not drop the lit match, and the pile remained unignited, this would also be compatible with S’s being true. So line 4 is vindicated.

Karl