Increasing FPS

If buying a new PC isn't an option you can try lowering the ingame settings and using the multithreaded options recommended above.
If you're willing to spend some money I'd recommend upgrading your CPU first if its not good, make sure to look at more than just core count and gigahertz, look at benchmarks on websites like userbenchmark.
If your CPU is good I'd say to get a better GPU and make sure to look at benchmarks for that too.

To decrease loading times you could buy a SSD. They're becoming cheaper and you can get 240 gb for less than $100 but it won't really help with FPS