Heroes 7 lags in the main menu.

If you reduce the screen resolution, will it run more stably?

In theory, yes. But specifically in the main menu, you might not even notice any improvements; it's a bit strange. It seems like you need to solve the issue using a firewall.
But overall, the game is demanding, unfortunately. I'll probably get flamed for saying this, but it would have been better if the developers had made the graphics in the style of Civ6, so that the strategy game wouldn't have such a high hardware requirement.