Hello, what needs to be done is have a suitable scan tool connected to read what fault codes have been stored.
Most likely is a faulty wheel speed sensor. If the fault has only occurred since the brake pads were done then the sensor could have been unplugged by mistake or damaged.
The rear handbrake will need to be adjusted to the correct setting to take up any excess slack.
it was like that before i change them. whe you first start to drive and you brake feels like there grinding then it clears but brakes feel hard then you can jump on them with out abs working
The grinding you feel is the ABS pump working. From the way you describe it happening just as you drive off indicates at least one wheel speed sensor is not working properly.