Set out a drinking glass, jar, or deep bowl with a large opening and pour in 3–4 inches (7.6–10.2 cm) of pure acetone. The container needs to be full enough to completely submerge multiple pieces of plastic. Choose a container that you don’t mind ruining in case you have trouble removing every last trace of plastic when your project is finished.  It’s critical that whatever container you use be made of a material like glass or ceramic. You want it to dissolve the plastic you’ll be using for, not the cup that’s holding it. Acetone is a hazardous liquid, it gives off powerful fumes, so be sure to work somewhere with good ventilation. Stir the pieces with a toothpick to help them settle. The should be totally immersed at the bottom of the container. If necessary, add another splash of acetone to cover the tops of pieces with irregular dimensions.  For a more natural looking repair job, try to find plastic in the same color as the item you're repairing. Avoid touching the acetone. It can cause mild irritation if it comes into contact with your skin. As it soaks in the acetone, it will slowly break down to form a thick, goopy slurry. The exact amount of time this takes will vary depending on the type of plastic you’re working with and how much you’re melting down. Play it safe and let it sit for at least 8-12 hours.  Cutting or breaking the plastic into smaller pieces may help speed things along. The more surface area it has, the faster the acetone will act on it.  The slurry should have a smooth, creamy consistency and be free of lumps or chunks before you attempt to use it to weld other pieces together. Do not dispose of the excess acetone in a sink or toilet bowl, it must be taken to a hazardous chemical disposal site. Put the excess acetone in a glass jar with a tightly sealing cap and dispose of it at an approved hazardous chemical disposal site. Drain the liquid into a glass jar so that only the plastic slurry remains. You’ll use this as a filler to make your repairs. It’s okay if there are traces amounts of...

TL;DR in Indonesian:
Isi wadah kaca dengan aseton. Letakkan beberapa potongan plastik di dalam aseton. Biarkan plastik terendam semalaman agar larut. Buang sisa aseton. Oleskan bubur plastik ke bagian yang rusak. Tunggu sampai plastik mengeras.