Thank's for clarifying and attempting the question. The online calculator on this page: Distance to the Horizon Calculator is close to the solution. On the calculator, the observer is at a known height and the distance is unknown. The diagram on that page is relevant. To calculate the height of the skyscraper, we need to switch the position of observer and object, as the observer is on the ground, and the viewed object is the top of the skyscraper. The radius of the Earth is needed for the calculation.
Working backwards, knowing that the height of the tower is 828 m, I calculate that it can be seen from about 102.7 km away (not 95 km). The Distance to Horizon Calculator's answer is consistent with this information. Using your value of 95 km, I got an answer of about 709.5 meters for the height of the tower. However, this answer is nearly 120 m (longer that a football field) too short.