[HELP] General Performance Question ?no FPS Changes

Hey! I have an Question…about something strange i have on my Project like 20-25 FPS on Full HD

Textures-Epic (i have some 4k Textures)
Shadow-Medium / when im Change it i get more FPS 3+ but just sometime)
Effect-High(No FPS Changes)
-Resolutionscale 50-80%

i have a Quality Menu from Marketplace so i can switch it Realtime in Game…but Doesnt Matter what i change even the Resolution there are no FPS Changes?

Sometimes i got +4 fps when im Play with ONLY “Resolution Scale” 80"

Now i was remove my Landscapes because i had more 8x8 k …,but there are even no Differences?

my PC Specs

Newest NVDIA Driv
Win 7 64x
GTX 750 TI OC
INTEL XEON HASW 3.4 GHZ
32 GB Ram

I know its a LOW END Graphic Card,…but when i have 20 fps on FULL HD, shouldn’t i get more when im Lower Some Settings? i see it the Quality Menu works fine , but no FPS Change?

i tryt like everything ,was deleting 2 of my Landscapes 8x8 K,but there also no Changes.

All are Dynamically Lighting.

I dont know , is this Normal?

Hope Someone can help me with this

Thanks!.

KS