That is such a broad and wildly inaccurate statement as to be best ignored.Most of the time it's insufficient RAM that causes this lagging problem.
1. Share Your Specs & Settings
If you're running into problems then unless it's well known the first thing that folk will ask you for are your rigs specifications and what graphical settings you have the game on. This helps to find if there is a common issue between your hardware and the game you're running. It saves time, trust me!
2. Be Precise About The Problem
If an game crash only occurs after turn 30 in a strategy game then it's worth sharing that info, the more precise you can be about the nature of the problem, the easier it is to solve.
3. What Provider Are You With?
This only really matters for those times when you're constantly disconnecting from multiplayer games. There are often links between the time you're playing and the problems and knowing who looks after your internet can really help pinpoint if that's the cause.
4. Remember We're All Human
There are no guarantees that a solution one person found will also work for you or that a known fix exists for your issue. It can be frustrating, but everyone responding is trying to help.
Did you uninstall your gpu drivers with DDU and reinstall them via amd/nividia website?
How do you do that