Why my Shadows are so expensive?

I started a new project of a tbs game 2 weeks ago, project without starter content. When I Use Scalability Shadows on Low (As I Can see Low=Disabled) I get 120fps, but if my shadows are medium high or epic (Enabled) my fps falls to 45, does anybody know how to solve this? How characters and blocks are made using only static mesh (all basic cubes) and the materials are as simple as possible.

Sorry for the bad english, still learning.

Scalability Shadows on Epic (Performance equals to high and medium)

Scalability Shadows on Low (I think it’s the same as disabled)

Another question: Is 120fps limited by default? How can I unlock the fps or set it to 240?

Edit1: MY characters and blocks are made using only static mesh.

What’s your machine spec?

You can unlimit the FPS with the console command: t.maxfps 500

Have you tweaked anything in the light settings?

I figured out the problem, all the blocks in the scene are using dynamic shadows, I really need independent blocks as I use them for path finding, so I just disabled dynamic shadow, thank you for the answer.