Chaissos is correct. The timing belt should not affect how the engine runs until the point at which it snaps–without warning. More likely is that poor maintenance is the cause of the shuddering while accelerating. Spark plugs, plug wires, and the fuel filter are some of the items that may need replacing.
Another possibility is that your fuel system may be gummed up. A bottle of one of the more potent fuel system cleaners may clear up the problem. I have no idea of what products are sold in Egypt, but if Chevron’s Techron product is available, I can recommend it highly. Shell also has a very good fuel system cleaner available in bottles, although I can’t recall the name of the product. Others, like the STP products, are not very effective.
If my memory serves me correctly, the replacement interval for Daewoo timing belts is every 6 years or 72,000 miles, whichever comes first. By that measure, if the belt is the original, you are treading on very thin ice with the belt in this 10-11 year old car. Since it has an interference design engine, when the timing belt snaps it will result in engine damage that would cost more to repair than the car is worth.
If you hope to keep driving this car, you should have the timing belt, water pump, serpentine belt, and all belt tensioners replaced right away. While it is in the shop for those procedures, have the mechanic bring all of the periodic maintenance up to date, and your shuddering problems should be over.