The sink will not clog if it is washed with hot water at least once a week.
In order for the drain hole to remain clean, do not pour fat into it, as it hardens in the soap and clogs the drain hole. Before washing the dishes, rub the fat with a rag and preferably paper. Drain the fat in any jar, and then, when it freezes, throw it away. Periodically clean the filter grid.
If the sink is still clogged, then the vantuz will help in this matter. Put it over the stock and press it as often as possible. If there is another hole above, then it must be clogged with something. It needs to be done in the same way if the sink is double. Removing blockage may not occur immediately as soon as you started to perform these actions, so you have to sweat to achieve the result, perhaps 10-15 minutes.
The following solution can be used to remove the blockage: pour into the stock ? soda glasses and pour ? glasses of vinegar. Pill you all holes and wait 5-10 minutes while the fats dissolve, then rinse with hot water.
If all these actions have not been successful, then contact plumbers who have a special tool (plumbing drill) for such cases.