Kia Picanto Ba 1.1 Brake cannot be used

Hello, I’ve been having the problem for a few months that my brake doesn’t work properly. If I drive slowly (0-35KMh) and brake my brake doesn’t work every now and then, I brake and it only ratters if I go off the brake once completely and again it brakes normally. The problem doesn’t always occur. This morning I could only push the brake two centimeters and from there was the so-called block and the car didn’t brake even after I went off the brake once. I was already in the workshop but they didn’t find anything My brake pads are new and the brake pads still look good. I don’t know what it might be and ask for help. Thank you very much.