diff --git a/main.cpp b/main.cpp
index b90476f..3f68015 100644
--- a/main.cpp
+++ b/main.cpp
@@ -16,8 +16,8 @@ int main(int argc, char *argv[])
 
     cout << "Bonjour et bienvenu" << endl;
     
-    Network network(2, 5);
-    network.forward({1.0,1.0,1.0,1.0,1.0}, {1.0,1.0,1.0,1.0,1.0});
+    Network network(3, 3);
+    network.forward({1.0,1.0,1.0}, {1.0,2.0,3.0});
     network.print();
 
     /*Neuron n(3), n1(1), n2(1), n3(1);
@@ -37,6 +37,6 @@ int main(int argc, char *argv[])
     {
         cout << *it << endl;
     }*/
-    
+
     return 0;
 }
diff --git a/myclasses.cpp b/myclasses.cpp
index 7b0067e..cb15479 100644
--- a/myclasses.cpp
+++ b/myclasses.cpp
@@ -44,6 +44,30 @@ float Neuron::get_derror()
     return derror;
 }
 
+void Neuron::set_nth_weight(int n, float value)
+{
+    int i=1;
+    forward_list<float>::iterator current_weight(weights.begin());
+    while(i<n)
+    {
+        current_weight++;
+        i++;
+    }
+    *current_weight = value;
+}
+
+float Neuron::get_nth_weight(int n)
+{
+    int i=1;
+    forward_list<float>::iterator current_weight(weights.begin());
+    while(i<n)
+    {
+        current_weight++;
+        i++;
+    }
+    return *current_weight;
+}
+
 void Neuron::activate(forward_list<Neuron>::iterator &prev_layer_it, Activ activ_function)
 {
     weighted_sum = bias;
@@ -139,6 +163,7 @@ bool Network::forward(const std::vector<float> &input, const std::vector<float>
             }
         }
     }
+    set_errors(target);
     return true;
 }
 
@@ -160,13 +185,16 @@ bool Network::set_errors(const std::vector<float> &target)
         {
             list<forward_list<Neuron>>::reverse_iterator temp_next_layer = current_layer; //temp_next_layer set at current layer
             temp_next_layer--; //temp_next_layer set now at next layer
+            int neuron_counter=0;
             for(forward_list<Neuron>::iterator current_neuron(current_layer->begin()) ; current_neuron!=current_layer->end() ; ++current_neuron)
             {//inside current neuron
+                neuron_counter++;
                 current_neuron->set_derror(0.0);
                 for(forward_list<Neuron>::iterator next_layer_current_neuron(temp_next_layer->begin()) ; next_layer_current_neuron!=temp_next_layer->end() ; ++next_layer_current_neuron)
                 {
-                    //
+                    current_neuron->set_derror( current_neuron->get_derror()+next_layer_current_neuron->get_derror()*next_layer_current_neuron->get_nth_weight(neuron_counter) );
                 }
+                current_neuron->set_derror( current_neuron->get_derror()*Tools::activation_function_derivative(h_activ,current_neuron->get_weighted_sum()) );
             }
         }
     }
@@ -175,6 +203,26 @@ bool Network::set_errors(const std::vector<float> &target)
 
 bool Network::backward(float learning_rate)
 {
+    int layer_counter = layers.size()+1;
+    for(list<forward_list<Neuron>>::reverse_iterator current_layer(layers.rbegin()) ; current_layer!=layers.rend() ; ++current_layer)
+    {//inside current layer
+        layer_counter--;
+        if(layer_counter>1) //all layers except input layer
+        {
+            list<forward_list<Neuron>>::reverse_iterator temp_prev_layer = current_layer; //temp_prev_layer set at current layer
+            temp_prev_layer++; //temp_prev_layer set now at previous layer
+            int neuron_counter=0;
+            for(forward_list<Neuron>::iterator current_neuron(current_layer->begin()) ; current_neuron!=current_layer->end() ; ++current_neuron)
+            {//inside current neuron
+                neuron_counter++;
+                for(forward_list<Neuron>::iterator prev_layer_current_neuron(temp_prev_layer->begin()) ; prev_layer_current_neuron!=temp_prev_layer->end() ; ++prev_layer_current_neuron)
+                {
+                    //current_neuron->set_nth_weight()
+                    current_neuron->set_derror( current_neuron->get_derror()+prev_layer_current_neuron->get_derror()*prev_layer_current_neuron->get_nth_weight(neuron_counter) );
+                }
+            }
+        }
+    }
     return true;
 }
 
@@ -221,12 +269,14 @@ void Network::print()
             cout << (">> Output layer\n");
             cout << "size : " << current_layer_size << endl;
             cout << ("neurons' activations : ");
-            for(forward_list<Neuron>::iterator it2(it1->begin()) ; it2!=it1->end() ; ++it2){cout << it2->get_activated_output() << " ";}
+            //for(forward_list<Neuron>::iterator it2(it1->begin()) ; it2!=it1->end() ; ++it2){cout << it2->get_activated_output() << " ";}
+            for(forward_list<Neuron>::iterator it2(it1->begin()) ; it2!=it1->end() ; ++it2){cout << it2->get_activated_output() << " " << it2->get_derror() << endl; for(int i=1;i<=3;i++){cout << it2->get_nth_weight(i) << " ";}cout<<endl;}//to be deleted
             cout << endl;
         }else
         {
             cout << ">> Hidden layer " << layer_counter-1 << endl;
             cout << "size : " << current_layer_size << endl;
+            for(forward_list<Neuron>::iterator it2(it1->begin()) ; it2!=it1->end() ; ++it2){cout << it2->get_activated_output() << " " << it2->get_derror() << endl;}//to be deleted
         }
         cout << "------------------------------------------------" << endl;
     }
diff --git a/myclasses.h b/myclasses.h
index 223c77f..a34a196 100644
--- a/myclasses.h
+++ b/myclasses.h
@@ -21,6 +21,9 @@ public:
     float get_activated_output();
     void set_derror(float value);
     float get_derror();
+    void set_nth_weight(int n, float value);
+    float get_nth_weight(int n);
+    //std::forward_list<float> &get_weights();
     void activate(std::forward_list<Neuron>::iterator &prev_layer_it, Activ activ_function=LINEAR);
 private:
     std::forward_list<float> weights;