JSFiddle - React, Tailwind, and code Playground

HTML

<form id="TWRechner">
		<legend>TW</legend>
		<p></p>
	
<table>

		<input type="number" data-index="1" min="0" id="skill1"  value=""><output id="betrag1"  for="">0</output>
	
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/catch_safety.gif" alt="x">&nbsp
		<label for="skill1">Fangsicherheit</label>
		
		<input type="number"data-index="2" min="0" id="skill2" value=""><output id="betrag2" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/penalty_area_safety.gif" alt="x">&nbsp
		<label for="skill2">Strafraum</label> 
	
		<input type="number" data-index="3" min="0" id="skill3" value=""><output id="betrag3" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/fitness.gif" alt="x">&nbsp
		<label for="skill3">Fitness</label>
	
		<input type="number" data-index="4" min="0" id="skill4" value=""><output id="betrag4" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/speed.gif" alt="x">&nbsp
		<label for="skill4">Geschwindigkeit</label>
		
		<input type="number" data-index="5" min="0" id="skill5" value=""><output id="betrag5" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/duell.gif" alt="x">&nbsp
		<label for="skill5">Zweikampf</label>
		
		<input type="number" data-index="6" min="0" id="skill6" value=""><output id="betrag6" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/endurance.gif" alt="x">&nbsp
		<label for="skill6">Ausdauer</label>
	
		<input type="number" data-index="7" min="0" id="skill7" value=""><output id="betrag7" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/shot.gif" alt="x">&nbsp
		<label for="skill7">Schuss</label>
		
		<input type="number" data-index="8" min="0" id="skill8" value=""><output id="betrag8" for="">0</output>
		&nbsp <img src="http://fussballcup.de/designs/redesign/images/icons/two_footed.gif"...

CSS

form {
    
	border: thin solid #666;
	width: 27em;
	padding: 1em;

}

legend {
	font-size: 1.5em;
	margin-bottom: 1em;
}

input[type=number] {
	text-align: auto;
}

label,
span,
output {
	display: inline-block;
}

form p {
	font-weight: bold;
}

output {
	width: 4em;
	text-align: right;
}

		img {
  width: 5%; 
  height: auto;
}

JavaScript

$('#TWRechner').on('keydown', 'input', function (event) {
    if (event.which == 13) {
        event.preventDefault();
        var $this = $(event.target);
        var index = parseFloat($this.attr('data-index'));
        $('[data-index="' + (index + 1).toString() + '"]').focus();
    }
 });

		document.addEventListener('DOMContentLoaded', function () {
			function rechne() {
				var skill1 = document.getElementById('skill1'), 
					skill2 = document.getElementById('skill2'),
					skill3 = document.getElementById('skill3'),
					skill4 = document.getElementById('skill4'),
					skill5 = document.getElementById('skill5'),
					skill6 = document.getElementById('skill6'),
					skill7 = document.getElementById('skill7'),
					skill8 = document.getElementById('skill8'),
					skill9 = document.getElementById('skill9'),
					skill10 = document.getElementById('skill10'),
					skill11 = document.getElementById('skill11'),
					skill12 = document.getElementById('skill12');
			
          			var summe1 = skill1.valueAsNumber / 28 * 5;
				    summe1 = summe1.toFixed(3);
				    document.getElementById('betrag1')
					.value = summe1;
	

					var summe2 = skill2.valueAsNumber / 28 * 5;
					summe2 = summe2.toFixed(3);
				    document.getElementById('betrag2')
					.value = summe2;
					
					var summe3 = skill3.valueAsNumber / 28 * 4;
					summe3 = summe3.toFixed(3);
				    document.getElementById('betrag3')
					.value = summe3;
					
					var summe4 = skill4.valueAsNumber / 28 * 3;
					summe4 = summe4.toFixed(3);
				    document.getElementById('betrag4')
					.value = summe4;
					
					var summe5 = skill5.valueAsNumber / 28 * 2;
					summe5 = summe5.toFixed(3);
				    document.getElementById('betrag5')
					.value = summe5;
					
					var summe6 = skill6.valueAsNumber / 28 * 1;
					summe6 = summe6.toFixed(3);
				    document.getElementById('betrag6')
					.value = summe6;
					
					var summe7 = skill7.valueAsNumber / 28 * 1;
					summe7 = summe7.toFixed(3);
				   ...