My game suddenly during live mode started acting out. The only theory i have is overusing "Make active" option on MC but I'm not quite sure. Before that I recall downloading only a bit CC clothes and checked if they're not for sims 4.I firstly reset everything in city hall using MC. I removed all the game mods but nothing had changed. What do you think is the issue?

Of course everything I've read says "clear your caches". Did you try that?

Yes,and it doesn't work. After that, I removed the whole The Sims 3 folder and ran the game so it creates new files and it's back to normal, but I don't want a new game. Then I just added the Saves folder with the new files but the game won't let me run because of some data that belongs to a EP (I haven't touched any EPs). I then tried to run it only without CC and it opens very fast and smooth without it but it's back again. I think in the end is best to copy all the sims I want to keep in the library and start fresh in the same world, just like when moving in.

I have it luckily, what do you think it might be the issue so I could prevent it?

I've actually fixed it today. I simply copied my family into the clipboard with their house, restarted the game with only saving cc and library files. Then I started the new game in the same world but restarted as if It was never played and moved all of my families. It works smooth and normal.
My laptop is strong from last year with Win10 64bit and 8GB RAM but my world is large (Alpine County) with a lot of cc and I still experience lagging, maybe that can trigger corruption, idk.
Tanks for the tip about saving, I didn't know that, it kinda sucks since my game is loading in total about 20 min.

Alpine County is a custom world that is too large and intricate to play well on most any system. It doesn't matter how much RAM we have after a certain point, the game engine just cannot handle that kind of stress very well and ~3.7 GB is the limit as to how much the game can work with per session.

Mentioned near the beginning -- using MasterController to switch between active households. That's fine, but if these household switches are set to be Dream Catching, then the sims not actively being played will still have their Dream Managers running. That can be a huge drain on RAM usage and performance. MC can bet set to be Dream Catching or not. To see how many sims/households have DMs running on them, on City Hall or an in-game computer NRaas > MC > Sim > Basic > Family Tree (or something harmless like that) > (Filter to Has Dream Manager). To switch off DMs on all but the actively being played sims, unfortunately it's all or nothing, MC > Town > Drop All Dreams and Opportunities (the active household will not be affected).