after the new update the system lags
Okay. You gonna give us more to chew on or is that it?
Hiya mate, it would be really helpful if you gave a bit more information other than "the system lags". What exactly is happening, what are the specific differences you notice between now and before the update etc? If you give a bit more information (like @Kytharsis asked for...), folks might be better able to help you....
Give it a bit of time, if you have only just updated, Android is still optimising apps. Sometimes it can take a bit of time. Restart your phone a couple of times over the next couple of hours, run through 1 or more charge cycles. You will find that many issues will correct themselves.
The likes of some Google apps such as Playstore will update in the background. It can just take a little time for the sequence to complete and settle down.
It's just Android 10 doing it's thing.
Nouvelle fonction OxygenOS : la Charge Optimisée
by Vito B., 2020-01-07