Hello,
did you already look to the datasheet. Under switching characteristics, there's a core performance chapter. Besides maximum core clock, I would particularly refer to DSP and memory block specs. Even if a core clock of e.g. 500 MHz is feasible, you can't operate DSP or memory blocks at this clock rate.
Second point is to find useful clock speed versus logic complexity tradeoff for your design. Length of combinational path between registers defines the maximal clock speed. Pipelining can help to increase speed by dividing logical and arithmetic operations in multiple steps, utilizing additional registers and increasing latency. For Cyclone V, arithmetic unit clock rates without extensive pipelining are more in a 50 to 100 MHz range.
Suggest to setup a snippet of your intended logic and experiment with clock rates and pipelining.
Best regards
Frank