Kao Kao learning to sit for treats (he is 10 lol)

So I started training Kao Kao last month. He is 10 years and 6 months old, a mix cat who thinks he is a dog. My mum says it is too late for old cat to learn, I said we will see. He know the word treat already, he come running when I open the bag. Good start. We use a clicker from the pet shop near the BTS, and a small chicken stick. First I click when he sits, but he just stand up and look at me like I am stupid. After 3 days he sit for 2 seconds. Then 5 seconds. Then he sit and yell at me because the treat is slow. The hardest part is he not like the sound of clicker. Every time I click he run to the bedroom and hide under the bed. I changed to a small click of my tongue, that works much better. He come back out after 10 min and sit next to me. Im 17 and my school exam is in 2 weeks so training happen in the evening only. Kao Kao is lazy in the morning but in the evening he is very active, like he is my study buddy.