Good evening,
Laptop with Dual Boot: Win 10 + Linux Mint 19.3 (Tricia)
CPU: i7
Graphic Card Nvidia

since yesterday, on my laptop, at the end of Grub procedure, I've got a black screen and the system has got stuck. I suppose there's something wrong with my Graphic Card settings.
if I start Win 10 or if I use a Linux Mint Live USB, everything is ok .

Please give me a help!
Best regards
Beppe

After GRUB, press Function2 (F2) button, do you see the text? Any errors?

I may be way off since I find Grub WAY too complex for doing one job and doing it well but I'm nearly certain there is some equivalent to [Option = "nomodeset"] so that bootup/kernerl load text never fails. At least then you can see error messages or if you're just a tad too impatient. I've never understood why some folks prefer some splash screen or fonts too small to read. The kernel loading is literally "where the rubber meets the road". BTW I'm not referring to you but to distro developers. Give me human readable logs and runlevel 3 and I'm happy.

I've pressed F2, but nothing happens. I can see some text for a flash and then I can just see a small blinking horizontal cursor on the high left corner of the screen.
No text!
In order to switch off the PC I have to keep the on/off key for a while...

It is common for the Power Switch to require 4 seconds before shutoff. It might be wise to research Grub options to make certain you're set to display boot text instead of some splash screen or blank screen. Of course you could boot the USB stick and then follow procedure to chroot into your installed system and update-grub.

Here's an example for kernel repair but chroot is identical. https://forums.linuxmint.com/viewtopic.php?t=215393

I can choose recovery mode and insert command through Text as root user

I followed the procedure for Kernel repair, but without any result.
Since I installed Linux Mint just a couple of day ago, I could reinstall everything in order to solve the problem.

Well; so when you first installed Mint, did the desktop environment worked, for how long? and what changed that caused it to stop working? Did the automatic (or manual) updates caused this?

Actually I reinstalled Linux Mint and now it's working fine except for audio output.