Answer: False
Explanation: What this statement describes is not a trapezoid, but rather a kite. A kite is a quadrilateral with two sides that are next to each other (ie adjacent) that are congruent. This is the result of combining two congruent triangles together. The diagonals of any kite are perpendicular, which is another way of saying "the diagonals have slope that are negative reciprocals".
If you had adjacent sides congruent, and a pair of parallel opposite sides, then the other two opposite sides must be parallel as well, but this would make the figure a parallelogram and not a trapezoid. This is another way to see why the answer is false.
Check out the attached image for an example.