Initialize TeX Live User Mode

1. Initialize User Mode:

   tlmgr init-usertree

2. Install nccmath Package: After initializing the user mode, you can install the nccmath package:

   tlmgr install nccmath

Complete Steps

1. Initialize User Mode:

   tlmgr init-usertree

2. Install nccmath Package:

   tlmgr install nccmath

3. Verify Installation: You can check if the package is installed correctly by running:

   tlmgr list | grep nccmath

Once you have initialized the user mode and installed the package, try compiling your main.tex file again in TeXmaker.

Troubleshooting

If you still face issues, you might need to install TeX Live with the full package set:

sudo apt-get install texlive-full

This command installs all TeX Live packages and ensures that you have everything you need to compile most LaTeX documents.

After completing these steps, try compiling your document again. This should resolve the errors related to the Babel package and the missing nccmath package.

Correct the Babel Language Option

Change the option 'polish' to 'polski' in your LaTeX document.

Install the Missing nccmath Package

Since you encountered an issue with tlmgr on Debian, you might need to install the package via the package manager or manually. First, let's try the package manager method.

Method 1: Using APT (Debian/Ubuntu)

You can try installing all LaTeX packages, including nccmath, by running:

sudo apt-get install texlive-latex-extra

This command installs additional LaTeX packages that are often required.