Hi Savsir, idk if it's a11 havoc you're using but the interface is slow, there are lot of lags. Especially when I lock the phone. The UI responses up to 5 sec later. Maybe I've installed havoc 4 wrong
-Wipe data, system, vendor, cache, dalvik cache
-Flash havoc 4.1
-Flash gapps (optional/I recommend flame gapps)
-Flash magisk (optional)
If you do this and still lag you can try format data (first backup pc) maybe thats reason. I never tried without format data.
The only thing I didn't do is wiping the vendor part. Some devs say that it's useless to do it so I don't used to do. Also, I installed the latest cepheus firmware before installing the ROM. I will give a try later. I'm busy for now