Problem with fps

[Pipum]

Well how the title says i can see what in some maps my memory clock and another things download to 500 for example, my video card have 1143 memory clock but in some maps like one raid fighter or bosses my gpu only uses 500 memory clock and a half of the recurses and idk why, this kill my fps :/.

 

In another maps i can see how i play with 80 fps and on bosses is like 20 30 fps for this.

 

I have one gtx 760.

 

And sorry for my english i speak spanilsh :p.