Based on the answers provided, the following corrections need to be made to the 3D object:

1. The object should be redesigned to resemble a right triangle. This means it should have two sides that meet at a right angle and a third side that connects the ends of the first two sides. 

2. The object should only have three sides. Currently, it has more than three sides due to its pentagonal top and rectangular base. The new design should only include three sides to form a right triangle. 

Please note that the object should still be extruded in one dimension and have one angle that is 90 degrees, as these aspects are already correct.