Using multiple rows and spacing

Since you are new to the world of LaTeX tables, I will give you my recipe.

First, LaTeX is for producing beautiful print materials or slides. For actual work with numbers, I use excel. (Other people will use R or some other statistics package.)

While in the spreadsheet you can do calculations, reorder columns, put color in titles or cells, set the lines, etc. until you get the final result, according to your taste or the original you are reproducing or the style that you must comply with for a final report or thesis.

Then you go to LaTeX. You can manually enter the table cell by cell, row by row, or export it from its source (strongly recommended).

I use an Excel add-in excel2latex that produces (almost) the final code. The most important part is that it will faithfully export the content, so nothing is lost in translation.

https://ctan.org/pkg/excel2latex?lang=en

Copy to clipboard and paste it into your LateX code. It will compile without errors. (In this case you need to add the package booktabs).

Then you can work with the too-many LaTex packages dedicated to tables to fit the table to the page, change the style, etc. But most importantly, the original content will remain intact!

For this example, I added the shorter column rules and the caption (cut and paste from original). Other embellishments remains for the reader. :)

documentclass[landscape]{article}
usepackage{booktabs} %required
usepackage{multirow} %not needed here but useful
usepackage{geometry} % to fit the table in the page

begin{document}

% Table generated by Excel2LaTeX from sheet 'Sheet1'
begin{table}[htbp]
    centering
 caption{Breakdown by Voivodeship}
    begin{tabular}{lccccccc}
        toprule
        textbf{Voivodeship} & Total Cases & Cases 100k & Total Deaths & Deaths 100k & Total Tests & Total Tests & Case Fatality 
         cmidrule(r){1-1}cmidrule(lr){2-2}cmidrule(lr){3-3}cmidrule(lr){4-4}%
        cmidrule(lr){5-5}cmidrule(lr){6-6}cmidrule(lr){7-7}cmidrule(lr){8-8}
%       midrule
        Lower Silesia & 1100  & 1.15  & 1.25  & 1.45  & 1     & 220   & 20 
        Kuyavian-Pomeranian & 1.5   & 1.8   & 1.9   & 2.2   & 1.5   & 20    & 20 
        Lublin & 2     & 2.3   & 2.5   & 2.9   & 2     & 20    & 20 
        Lubusz & 3     & 2.9   & 3.1   & 3.6   & 2.5   & 20    & 20 
        Lodz  & 3.5   & 3.5   & 10.8  & 4.3   & 20    & 20    & 20 
        Lesser Poland & 3.5   & 3.5   & 3.8   & 4.3   & 20    & 20    & 29 
        Mazowieckie & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Opole & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Subcarpathian & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Podlasie & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Pomorskie & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Silesian & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Pomorskie & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Pomorskie & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Pomorskie & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        Silesian & 3.5   & 3.5   & 3.8   & 4.3   & 3     & 264   & --- 
        bottomrule
    end{tabular}%
    label{tab:addlabel}%
end{table}%

end{document}