The UE4 doesn’t run very well on laptops especially with GT GPUs e.g I get 50-60 fps with my gtx660 M
But you could try this:
-run your PC on the “high performance” power setting
-check if you really use the GT555M → e.g my laptop has a intel and a nivida graphic card-.I always have to choose the nivida (you can change that in the nvidia control pannel)