What Causes Severe Hair Fall Post Hair Smoothing Treatment?

I need a help and advice from you. Three months back i have done smoothening treatment in a salon. The person was not experienced at all. I had curly frizzy n very thick hair. He used R1 cream on my hair And left it for 1.15 hours because it was not working. After washing after 3 days, my hair became curly again. The cream has not worked. So he told me to do that treatment again in one week. And the next tym he used glatt R1 cream. Again the cream was not working so he left it for 1.30 hours. My hair was straight for 15 days only. Then they became wavy and i have started having too much hairfall since the last 3 months. I am so worried, my hair thickness have become so less. Please advice me what should i do.