oh, lol

no, I got steam version

For starters, you could check current FPS: enable debug, ctrl-d is the key. Not sure if it still works in EE, though.
Alternatively, go back to classic.

Nope. I just started the game

Try the Steam or Beamdog forums.

It could be a lot of reasons, from drivers to background processes.

You can try the following:

- change in games options to alternate renderer
- find and install latest drivers for the video card
- disable anti-virus
- open task manager and see if there any intensive processes, kill them

I have found the EE stuttering and lagging even on a very performant laptop (i7, 8Gb RAM, SSD) which means it is very un-optimized compared to the originals.