Nvidia GPU is not workin on Ubuntu 18.04.3

I'm running Ubuntu 18.04.3 with pantheon desktop, I installed the Nvidia drivers with the following command:

$ sudo apt install nvidia-driver-440

After the process was completed I restarted my pc. Now the NVIDIA X Servers Settings are installed and the app center shows the driver was successfully installed, but when I try to change the main GPU with prime settings, it doesn't work. Prime settings Additional drivers settings

I ran the following command to figure out what GPU is really working. This is what I get:

$ glxinfo|egrep "OpenGL vendor|OpenGL renderer"
OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) UHD Graphics 620 (Kabylake GT2)

I don't know if I have followed any wrong procedure. Thanks for your help!

Computer specs:

CPU : Intel® Core™ i5-8250U CPU @ 1.60GHz

GPU: Intel Corporation UHD Graphics 620 (rev 07) NVIDIA Corporation GM108M [GeForce MX130] (rev a2)

Edit: This is what I get from running the following command.

$ lspci -k | grep -EA3 'VGA|3D|Display'
00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07)
Subsystem: Acer Incorporated [ALI] UHD Graphics 620
Kernel driver in use: i915
Kernel modules: i915
--
01:00.0 3D controller: NVIDIA Corporation GM108M [GeForce MX130] (rev a2)
Subsystem: Acer Incorporated [ALI] GM108M [GeForce MX130]
Kernel driver in use: nvidia
Kernel modules: nvidiafb, nouveau, nvidia_drm, nvidia

And this one:

$ mokutil --sb-state 
SecureBoot disabled

Edit: I am going to write down some terminal commands that are shown in comments.

$ env |grep GDMSESSION
GDMSESSION=pantheon

And this one:

$ echo $XDG_SESSION_TYPE
x11