cannot install system

[Igor soln]

Hello dear support,
While installing the system Ubuntu 20.04 LTS,the error appears and cannot finish the installation.
The installer cannot install one file or i dont know what is it, its called grub.
Moreover, I have already deleted the system i was using previously (windows 10) and computer is unusable( I chose option try ubuntu, thats why i can communicate with you). I will add that im a beginner in linux systems, that would be my first os. Im counting on your help, thanks.If you have any questions, that would help you solve the problem,please ask away. Apologies for bad english.
Best wishes,
Igor from Poland

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445
Date: Sun Sep 6 16:29:11 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)