Ubuntu Mate is really slow

Yea - im a bit confused.
I remember the Raspberry PI 3 was already really fast with normal stuff.
Now i bought the RPi4 and downloaded Ubuntu Mate from this site:

After installing, rebooting and stuff it still feels slow opening programs and other stuff like browsing. Didnt experienced the problem with RPi3 in these terms

Its the RPi 4 with 4GB RAM that im using

Im also no 'Linux Pro' or something. But this...'lagginess' i didnt experienced with other versions. Any Ideas why this is happening?

Hi Kael mine is a little like that sometimes. I found when I had a browser open with a couple of tabs the pc became unresponsive, sound familiar? In my case, my 4gigs ram were all used up and the kernel was swapping out to disk. How to tell?
open a terminal window with: superkey t
type command: free -h
and see if any swap is used. Richard.