First of all really thanks for your time 
Yea the Rx pin uses a voltage divider and it's connected to Tx pin on the Nano.
Actually i am not using an application on my phone but a program on my pc that i made with node js, so the problem might be also here.
What the application does is to create a connection with my hc-05 and then start sending the string every 1 milliseconds. It then prints what receives from the hc-05.
I have now tried to increase the interval between each string, can 1 milliseconds be too fast? It works if i set an interval of 100 milliseconds but i really need to send data much faster than that rate (at max 10 milliseconds i think?).