@Einstasia Don't worry about the late reply; it's never a problem.
There are in-game issues (bugs and glitches) that can create the time lag you've described. But I haven't heard of a current one that happens when an active sim gets a roommate. So I think what instead might be going on here is that your processor isn't keeping up with the demands the game is placing on it. The CPU is weak for Sims 4, albeit (barely) above the minimum requirement, and it also has to do all the graphics processing. So it could certainly fall behind.
What you can try is playing with absolutely nothing else running at the same time. Restart your computer, open Origin, put it in offline mode unless you need to use the Gallery, and then launch the game. Don't even open a browser window or a music app; let the processor run only the game.
If you still see the same time lag, try playing in a clean boot:
https://www.windowscentral.com/how-clean-boot-windows-10
While it might be annoying to play like that going forward, trying it once would at least give you an idea of whether minimizing the load on the CPU could help, and it might also make clear whether this is in fact the issue.