i dont have discord , but when i m running vlc media player after tht my screen will start stopping frequently and tht will be increasing ...after an hour screen will stop in every 2 sec ....
and also i hv installed ubuntu unity DE ...on that there is no lag
What is the output of inxi -t cm ?
terminal said inxi not found 
Install it with the suggestion given by the terminal: sudo apt install inxi
milesdreaa@milesdredd-hp-notebook:~$ inxi -t cm
Processes: CPU: % used - top 5 active
1: cpu: 12.8% command: gnome-shell pid: 1695
2: cpu: 10.2% command: chrome pid: 16013
3: cpu: 6.1% command: skypeforlinux pid: 14483
4: cpu: 5.6% command: gnome-control-center pid: 16121
5: cpu: 5.3% command: Xorg pid: 1516
Memory: MB / % used - Used/Total: 1910.7/3377.1MB - top 5 active
1: mem: 259.69MB (7.6%) command: gnome-software pid: 2618
2: mem: 242.78MB (7.1%) command: gnome-shell pid: 1695
3: mem: 237.34MB (7.0%) command: chrome pid: 15467
4: mem: 230.32MB (6.8%) command: gnome-control-center pid: 16121
5: mem: 188.11MB (5.5%) command: skypeforlinux pid: 14483
Can you run it when you're running VLC? Currently, the CPU and RAM uses are low.
Two more things:
heyy, now its working fine ....and not lagging and
tht screen were flashing in vlc when i m moving its seek ....but now all running well .....
and also my pc ruing smoother after too many rebooting ,
and also ther are no any aditional drive installed for graphics 
I will assume you installed VLC using the software store or terminal, not any external download.
Would you mind still monitoring and updating this thread if you get the lag again? I appreciate your marking as solved but it would be good to know that we've definitively identified and eliminated the cause of the lag.
just now my laptop is lagging ....and i ran tht command inxi -t cm
what should i do??
and also by closing "soffice.bin" from system monitor ...pc started working smoothly
Somebody else is having lagging issues with VLC as well. Rather post it all over again, I am going to simply link you to my post...
Looks like you caught it. But I didn't expect soffice.bin to be the culprit. Can you check your version by posting here the output of libreoffice --version ?
Terminal says :-
:/$ libreoffice --version
LibreOffice 6.4.6.2 40(Build:2)
But every time screen start stopping due to different reason ... Somtime vlc and sometimes due to libre office .... Bcoz , i remembered ... At the very first when screen started stopping frequently , i didn't opend libre office
Your office version is the latest one for Z15. You’re saying that on inxi sometimes soffice is highest user and sometimes vlc is highest user, correct?
Would you mind also running lshw -c display ?
To make sure he gets all information, he should run it this way...
sudo lshw -c display
As an aside, I haven’t seen any difference when using it without sudo but it would be good to know if anyone does find differences.
It does make a difference. I had the windows side by side so you can't see everything, but you can see enough that running the sudo command shows you more. Additionally, in the other thread, running sudo command shares a ton more info on specs. 
wait ...
just now my pc was lagging ... then suddenlt it came to my mind to desable all extensions ...
and just after desabling all extensions from tweak .....there were no lag ...
so to find , which extension is doing this ?
by enabling one by one?
i dont want to desable all extensions ....
or may be i have to update all extensions ....
now i m going to update it firstly ...then i will inform wether it is lagging or not
that time(while checking vlc ) my pc was working well coz, i rebooted too manytime
and now still it was lagging...and after desabling all extensions it's not lagging
this time i m sure tht some extension are the culprit
Can you explain which extensions you’re referring to?
Hmm, tht i cant able to guess .... I turned off main switch of extension ...then my pc was working well .... And also i turned on some extension one by one ... Till that pc not lagged .... Today i will turn on all
I hv doubt on
impatience (mostly on this ).
custom hot corner
emoji selector
workspace scroll
as these are turned off now
