Our toilet's water filling section is filling very slowly and sometimes it gets stuck when pressed from inside and water keeps running.

About 6 months ago, we changed our toilet to a bidet toilet and the bidet faucet works very well. However, the current reservoir system fills very slowly and sometimes it gets stuck without the internal button being pressed and water runs to waste. The technician who installed the bidet toilet said at the time that the entire embedded system would need to be changed, but we couldn't proceed then because of both the system and having to break and reinstall it. We are looking for someone who could solve this in a simpler way. They mentioned on the internet that the mechanisms of this system get limescale buildup and those parts can be replaced, so we wanted to get help from here.