Recently I bought Uno voetstoot now my problem.

When the brakes lock up again, loosen the steel lines at the master cylinder. If the brakes release, look at the adjustment of the brake light switch to see if it's holding the pedal down a little. You can also verify that by loosening the nuts that hold the master cylinder to the booster. If the push rod in the booster is adjustable, check its adjustment.

If you loosen the master cylinder from the booster and the brakes don't release, but they do release when you loosen the steel lines, you have brake fluid contaminated with a petroleum product. The proper repair for that will likely exceed the value of the car.

If loosening the lines at the master cylinder does not release the brakes, that is good news because anything from there down is going to be less expensive. Open the bleeder screws on the calipers. If they release, suspect the rubber flex hoses.