That's disappointing to hear @Dandy__
My s²² Ultra is as snappy as when I took it out of the box and fired it up.
May I ask have you tried the generic tip of clearing the phone's System Partition Cache Files ?
> Clear Cache Files from the phone's System Partition Section > https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/ You may need to insert your earphones or hook upto a powered On Laptop to access the Clear Partition Section. This may help with lag or stutters as this clears the phone of old/unused or broken cache files.There is also a Repair Apps option in the Menu System too.
Do you use the optimisation tool in the Battery and Device Care.
Make sure your apps in the Playstore and Galaxy Store are updated and the phone is on the latest version available at the time.
Some who used Smartswitch to move their info from their previous phone to the new phone have experienced such issues.
As a last resort you could consider backing up and factory reset.
I wish you all the best. 
