How to effectively downscale input voltage of a device?
This question belongs to extensive area of engineering of data acquisition systems and instrumentation. The signal scaling is usually done in two steps: probe attenuator, and scope amplifier.

To begin, there is no such thing as "500V" and "GHz", this kind of signal will likely fry everything around and can be found only in high-powered RF antennas, where different methods are used to observe signals.

So you have mostly either "400 V" and few hundred kHz, or GigaHerz at 1-3-5V scale.

The first problem is solved by scaling the signal using 1:10X or 1:100X passive voltage oscilloscope probes, which are essentially capacitance-compensated voltage dividers. To get an impression, look at this article. 



The second type of pre-scaling uses "active probes", which are a combination of ultra-fast operational amplifiers with fine tuned coaxial transmission lines.



In both cases the signal is brought roughly to +-5V range. The rest of scaling is done inside an oscilloscope using variable gain wide-band amplifiers frequently referred as "front-end", see example here.



So the whole thing is a bit more complicated than an ordinary operational amplifier.