Lags in the dungeons

I decided to install Skyrim Legendary Edition, installed everything as it should, patched it to the latest version, and the game in the dungeons gives out 15 fps with any graphics, although it shows 130-170 fps at maximum speed outside.
Hardware:
Processor: intel 4x core x 3.40 Ghz
Video memory - Nvidea Geforce 830m
ROM - DDR3 12 gb
The game lags cleanly, and with the assembly of mods.
I played on an old PC not so long ago, it had ddr2, 2 gb of RAM because of which there were crashes from the game, but there were no problems with lags.