I know, that the question is somehow subjective, but this is my 2nd document writing in TeX. Therefore I've not so much input about the variety of commands and I would be very grateful for some ideas or commands to create table. My idea was to reduce the amount of horizontal lines and use some.
You can find below the mentioned table
\documentclass[a4paper]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage{amsthm}
\usepackage{mathtools}
\usepackage{rotating}
\usepackage{threeparttable}
\usepackage{booktabs}
\begin{document}
\begin{sidewaystable}
\centering
\begin{threeparttable}
\renewcommand*\TPTnoteLabel[1]{\parbox[b]{19pt}{\hfill#1}}
\caption{Table}
\begin{tabular}{@{\extracolsep{5pt}} cccccccccc}
\toprule
Sub 1 & Ml1. & Ml2. & Ml3. & Ml4. & Ml5. & Ml6. & Ml7. & Ml8. \\
\midrule
$12.04.2010 - 07.03.2012$ & $0.6532$ & $0.4603\tnote{+}$ & $0.4635\tnote{+}$ & $0.4590\tnote{+}$ & $0.4586\tnote{+}$ & $0.4584\tnote{+}$ & $0.4601\tnote{+}$ & $0.4550\tnote{+}$ \\
$08.03.2012 - 04.02.2014$ & $0.6534$ & $0.4966\tnote{+}$ & $0.4747\tnote{+}$ & $0.4768\tnote{+}$ & $0.4764\tnote{+}$ & $0.4741\tnote{+}$ & $0.4737\tnote{+}$ & $0.4853\tnote{+}$ \\
$05.02.2014 -04.01.2016$ & $0.4913$ & $0.4443\tnote{+}$ & $0.4407\tnote{+}$ & $0.4321\tnote{+}$ & $0.4361\tnote{+}$ & $0.4298\tnote{+}$ & $0.4356\tnote{+}$ & $0.4531$ \\
$05.01.2016 - 04.12.2017$ & $0.4257$ & $0.3629\tnote{+}$ & $0.3515\tnote{+}$ & $0.3504\tnote{+}$ & $0.3849$ & $0.3572\tnote{+}$ & $0.3483\tnote{+}$ & $0.3646\tnote{+}$ \\
\hline \\[-1.8ex]
Sub2 & & & & & & & & \\
\hline \\[-1.8ex]
$12.04.2010 - 07.03.2012$ & $0.3053$ & $0.2458\tnote{+}$ & $0.2457\tnote{+}$ & $0.2432\tnote{+}$ & $0.2435\tnote{+}$ & $0.2433\tnote{+}$ & $0.2435\tnote{+}$ & $0.2499\tnote{+}$ \\
$08.03.2012 - 04.02.2014$ & $0.2848$ & $0.2116\tnote{+}$ & $0.2071\tnote{+}$ & $0.2058\tnote{+}$ & $0.2096\tnote{+}$ & $0.2074\tnote{+}$ & $0.2064\tnote{+}$ & $0.2078\tnote{+}$ \\
$05.02.2014 -04.01.2016$ & $0.3423$ & $0.2698$ & $0.2596\tnote{+}$ & $0.2567\tnote{+}$ & $0.2569\tnote{+}$ & $0.2551\tnote{+}$ & $0.2561\tnote{+}$ & $0.2638\tnote{+}$ \\
$05.01.2016 - 04.12.2017$ & $0.2833$ & $0.2117$ & $0.2078\tnote{+}$ & $0.2049\tnote{+}$ & $0.2166$ & $0.2066\tnote{+}$ & $0.2051\tnote{+}$ & $0.2048\tnote{+}$ \\
\hline \\[-1.8ex]
Sub 3 & & & & & & & & \\
\hline \\[-1.8ex]
$12.04.2010 - 07.03.2012$ & $0.3462$ & $0.2927$ & $0.2839\tnote{+}$ & $0.2823\tnote{+}$ & $0.2867\tnote{+}$ & $0.2832\tnote{+}$ & $0.2831\tnote{+}$ & $0.2934\tnote{+}$ \\
$08.03.2012 - 04.02.2014$ & $0.3962$ & $0.3092\tnote{+}$ & $0.2994\tnote{+}$ & $0.2996\tnote{+}$ & $0.3023\tnote{+}$ & $0.3008\tnote{+}$ & $0.2991\tnote{+}$ & $0.3030\tnote{+}$ \\
$05.02.2014 -04.01.2016$ & $0.4278$ & $0.3706$ & $0.3530\tnote{+}$ & $0.3520\tnote{+}$ & $0.3583\tnote{+}$ & $0.3525\tnote{+}$ & $0.3545\tnote{+}$ & $0.3690$ \\
$05.01.2016 - 04.12.2017$ & $0.5177$ & $0.4090\tnote{+}$ & $0.4001\tnote{+}$ & $0.3996\tnote{+}$ & $0.4322$ & $0.4047\tnote{+}$ & $0.3964\tnote{+}$ & $0.4019\tnote{+}$ \\
\hline \\[-1.8ex]
Sub 3 & & & & & & & & \\
\hline \\[-1.8ex]
$12.04.2010 - 07.03.2012$ & $0.3716$ & $0.2819\tnote{+}$ & $0.2868\tnote{+}$ & $0.2800\tnote{+}$ & $0.2855\tnote{+}$ & $0.2832\tnote{+}$ & $0.2828\tnote{+}$ & $0.2841\tnote{+}$ \\
$08.03.2012 - 04.02.2014$ & $0.3508$ & $0.2644\tnote{+}$ & $0.2591\tnote{+}$ & $0.2563\tnote{+}$ & $0.2593\tnote{+}$ & $0.2558\tnote{+}$ & $0.2561$\tnote{+} & $0.2602\tnote{+}$ \\
$05.02.2014 -04.01.2016$ & $0.4661$ & $0.3565$ & $0.3422\tnote{+}$ & $0.3389\tnote{+}$ & $0.3366\tnote{+}$ & $0.3366\tnote{+}$ & $0.3372\tnote{+}$ & $0.3435\tnote{+}$ \\
$05.01.2016 - 04.12.2017$ & $0.4081$ & $0.2930$ & $0.2922\tnote{+}$ & $0.2875\tnote{+}$ & $0.3060$ & $0.2893\tnote{+}$ & $0.2880\tnote{+}$ & $0.2865\tnote{+}$ \\
\hline \\[-1.8ex]
Sub 4 & & & & & & & & \\
\hline \\[-1.8ex]
$12.04.2010 - 07.03.2012$ & $0.8119$ & $0.5476\tnote{+}$ & $0.5478\tnote{+}$ & $0.5422\tnote{+}$ & $0.5398\tnote{+}$ & $0.5410\tnote{+}$ & $0.5422\tnote{+}$ & $0.5388\tnote{+}$ \\
$08.03.2012 - 04.02.2014$ & $0.6772$ & $0.4893\tnote{+}$ & $0.4705\tnote{+}$ & $0.4723\tnote{+}$ & $0.4744\tnote{+}$ & $0.4719\tnote{+}$ & $0.4723\tnote{+}$ & $0.4788\tnote{+}$ \\
$05.02.2014 -04.01.2016$ & $0.6374$ & $0.5269\tnote{+}$ & $0.5299\tnote{+}$ & $0.5186\tnote{+}$ & $0.5223\tnote{+}$ & $0.5175\tnote{+}$ & $0.5224\tnote{+}$ & $0.5355\tnote{+}$ \\
$05.01.2016 - 04.12.2017$ & $0.4530$ & $0.3661$ & $0.3514$ & $0.3502$ & $0.3908$ & $0.3559$ & $0.3459\tnote{+}$ & $0.3625$ \\
\bottomrule
\end{tabular}
\begin{tablenotes}
\footnotesize
\item Some notes.
\end{tablenotes}
\end{threeparttable}
\end{sidewaystable}
\end{document}