The only time I had grey screen is when I've had Docky set up with all my Firefox launchers and apps, but realized that I still had to keep Firefox launchers on the desktop, to activate them properly in Docky. With desktop icons set to no desktop icons in customize when you right click the desktop, will bring you back to a grey screen after booting back in.
Can you right click empty space on the desktop? Then left click customise, then left click Desktop Settings. The Desktop Layout box at the top should say
Show desktop icons on primary monitor only
If it says
Then you need to change it back to Show desktop icons on primary monitor only
Could you please also in a Terminal type
Copy and paste everything you see back here please? Do not worry it tells us what hardware you're running and nothing else. It gives us a clue as to what could be the problem, with your apps suddenly closing. 
On the picture of your Terminal, I see you have 7 flatpak apps and 6 snap packages. I'm wondering if it is any of those that are failing to stay open?
I can't do right click on empty space on Desktop.
Everything load slow when I execute it first time but not when I execute it again.
Applications like chrome and vnc start and then suddenly close no matter how many times I try to reopen them.
Even if I check on Task Manager the application is killed.
After running inxi -Fz
I get
makis_best@MS-7A34 ~ $ inxi -Fz
System: Host: MS-7A34 Kernel: 5.0.0-29-generic x86_64 bits: 64 Desktop: N/A
Distro: Peppermint Ten
Machine: Device: desktop Mobo: Micro-Star model: B350 GAMING PLUS (MS-7A34) v: 4.0 serial: N/A
UEFI [Legacy]: American Megatrends v: M.F0 date: 01/23/2019
CPU: 6 core AMD Ryzen 5 1600 Six-Core (-MT-MCP-) cache: 3072 KB
clock speeds: max: 3200 MHz 1: 1377 MHz 2: 1377 MHz 3: 1377 MHz
4: 1377 MHz 5: 1377 MHz 6: 1377 MHz 7: 1316 MHz 8: 1308 MHz 9: 1319 MHz
10: 1319 MHz 11: 1798 MHz 12: 1412 MHz
Graphics: Card: Advanced Micro Devices [AMD/ATI] Baffin [Radeon RX 460/560D / Pro 450/455/460/555/555X/560/560X]
Display Server: x11 (X.Org 1.20.4 ) driver: amdgpu
Resolution: 1920x1080@60.00hz
OpenGL: renderer: AMD Radeon RX 460 Graphics (POLARIS11, DRM 3.27.0, 5.0.0-29-generic, LLVM 9.0.0)
version: 4.5 Mesa 19.3.0-devel (git-b9994cb 2019-10-01 bionic-oibaf-ppa)
Audio: Card-1 Advanced Micro Devices [AMD] Family 17h (Models 00h-0fh) HD Audio Controller
driver: snd_hda_intel
Card-2 Advanced Micro Devices [AMD/ATI] Baffin HDMI/DP Audio [Radeon RX 550 640SP / RX 560/560X]
driver: snd_hda_intel
Sound: Advanced Linux Sound Architecture v: k5.0.0-29-generic
Network: Card: Realtek RTL8111/8168/8411 PCIE Gigabit Ethernet Controller
driver: r8169
IF: enp25s0 state: up speed: 100 Mbps duplex: full mac: <filter>
Drives: HDD Total Size: 2496.5GB (2.3% used)
ID-1: /dev/sda model: Patriot_Spark size: 256.1GB
ID-2: /dev/sdb model: ADATA_SU650 size: 240.1GB
ID-3: /dev/sdc model: ST31000340AS size: 1000.2GB
ID-4: /dev/sdd model: ST31000340AS size: 1000.2GB
Partition: ID-1: / size: 234G used: 14G (7%) fs: ext4 dev: /dev/sda2
ID-2: /home size: 916G used: 33G (4%) fs: ext4 dev: /dev/sdc1
ID-3: swap-1 size: 9.12GB used: 0.00GB (0%) fs: swap dev: /dev/sdb5
RAID: No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors: System Temperatures: cpu: No active sensors found. Have you configured your sensors yet? mobo: N/A gpu: 33.0
Info: Processes: 291 Uptime: 11 min Memory: 1229.9/16052.1MB
Client: Shell (bash) inxi: 2.3.56