I tested your solution a few minutes ago.
First I should say that I saw in the task manager that firefox is working but I can't open or close it by click.
When I pressed ctrl+alt+esc mouse cursor changes but then left click did not work.
I should add another strange thing when I click on icons of Firefox, terminal, etc in the bottom panel of the desktop the click works! But I could not click anything inside firefox like close, minimize icons, etc.
Have you tested your RAM and Graphics?
I can't understand what you mean. What could I do with RAM and Graphics?
I think he means running some diagonstic tool like shown in this video (it should be the same even if it says it's for Ubuntu). I assume there must be similar tools specifically for the graphics card?
Thanks. My boot mode is UEFI and when I press esc I can't see grub menu I only see a terminal that the word Grub is written.
Is there other way to test RAM?
I think you can access the Grub menu by holding the Shift key instead. That should take you to the menu as shown in the video where you can choose the memory tester. It's possible if the logo splashscreen goes by too quickly that you have to repeat the process.
If you are still out of luck you can try this other method, by running a similar utility using the command line. I’ve tried it before with very little success since it’s a manual process, you will have to specify how much memory you want to test, so it’s a bit of a hit and miss. You can check this article for instructions to both methods (scroll to the bottom for the manual method).
On a side note: every computer uses a different key to access the boot menu, so I would recommend trying other common ones e.g.: F2, F8, F12. It's a bit of trial and error which admittedly can be annoying after having to restart a few times.
You can maybe save some time from a quick online search using the make and model of your machine followed by "boot to uefi" or "boot to bios" (bios is a term is still used interchangeably with uefi).
If booting as UEFI, then esc or tab key should work. If booting as Legacy (MBR), then holding left Shift Key should bring the grub menu up.
Ah that's good to know! I always spend a few minutes trying out different combinations until I find the right now, I'll keep this one in mind 
I rebooted my laptop many times with no success.
F2,F8,F12, Fn+F8, Fn+F12, shift and tab key does NOT work.
Pressing Esc key opens a screen like a terminal with 'Grub>' word at the beginning of each line.
Pressing Fn+F2 opens BIOS of laptop and I checked again boot mode is UEFI
My problem with frozen screen still exists I don't know what to do 
This is my grub file:
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'
GRUB_DEFAULT=5
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""
# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"
# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"
GRUB_THEME=/usr/share/grub/themes/zorin/theme.txt
It is strange that I can't see the grub menu I have seen that menu before with other distros of linux many times. Why I can't see that? Should I customize something?
I updated one line of my grub file to
GRUB_TIMEOUT_STYLE=menu
and after I could only see a menu with 3 options. 1. Zorin 2. Advanced zorin 3. UEFI firmware settings
I commented that line
GRUB_TIMEOUT_STYLE=hidden
Now after pressing tab key I could see that menu with 3 options.
Yes, you addressed that rightly. You also might consider changing the Grub Timeout to "10" instead of "5".
The system is freezing on apps other than VS Code, correct?
Yes it freezes on Firefox too. Right now I wanted to answer your question and it freezes, only terminal and Firefox has been opened.
I changed grub Timeout to 10 and I commented this line GRUB_TIMEOUT_STYLE=hidden or put it there, or make it equal to menu but I can't see the grub menu I just see that menu I mentioned in my previous comment here.
I'm wondering if using a live USB would give you access to the memtest option. I'm seem to remember that option was available when you plug in the USB with the .iso image to test a distribution without installing it 
I tested your suggestion with usb flash with zorin 16 but it does not show memtest option it has only install or try zorin option.
It seems memtest is not available for uefi mode:
system installation - Can I boot memtest86+ if I'm using UEFI? - Ask Ubuntu
I changed boot mode to Legacy then I put the usb flash and boot from usb but again there was no memtest option
Oh, that might actually be the reason I never noticed (most of my computers are old enough to use BIOS).
The link to askUbuntu suggests using another tool that should work with UEFI, perhaps that's worth a try.
There was recently another thread where a user having similar problems found out that the issue was hardware related (link below). I mention this as a possibility since both Firefox and VSCode may be writing too often to disk and thus causing the problem. Although I must admit at this point I'm all out of ideas and just guessing...
Thanks a lot. It's interesting he had click problems like me and I guess it should be related to hardware I had zorin for about 5 months and only in the last month I had this issue. I have zorin on another old laptop and I have never seen such an issue.
I have SSD on this laptop.
Could a computer hardware engineer find if SSD or any other hardware is damaged or not?
Finding hardware issues with software is difficult and maybe it is not accurate.
I suppose someone with that kind of knowledge and the proper tools, may be able to diagnose what the problem is exactly. If you go the DIY route you can start with replacing the memory sticks, SSD, etc., yourself and find the issue through elimination.
You can also try to re-install the OS altogether or even a different distribution since there are sometimes small incompatibilities that may cause this type of issues as well.
Here I'm talking from experience, I have a laptop that's a bit old (~10years) and would get random issues for no good reason. Sometimes it would freeze, sometimes the mouse took a little longer to respond. I did swap the memory on that one, but still had issues so I went ahead and installed Linux Mint, and so far good.
This is not to say that Zorin is bad or anything. I also tried Elementary, Manjaro and EndeavourOS on that laptop previously and always had one issue or another. Such is life, sometimes things simply don't work out 
.
@zenzen This error happens again and this time instead of left clicking by my connected mouse I used left button of lenovo trackpad and the problem was solved!
So in this case maybe my mouse or some mouse settings has some problem.
Do you have any idea?
Is it some sort of special mouse, like for gaming or something? I suppose it's possible the drivers or something have some faulty behavior. No idea, to be honest 
It is a usual, old mouse.
Thanks for your help.
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