Kibana doesn't show german Umlauts correctly

Hello.

I use Filebeat to send logs to Logstash which forwards them to Elasticsearch and then to Kibana.
I have no filters active as I still need to figure out how to use grok.
The logs appearing in Kibana are not presented correctly as certain characters (umlauts) are replaced with a question mark, like shown on the attached screenshot.

For example there is w?hrend instead of während, or ausgef?hrt instead of ausgeführt.
I already looked for solutions, but the answers confuse me.
I read this post and magnusbaeck wrote
"I don't understand. If you declare a character set for your input plugin that matches the actual input text, won't Logstash do the right thing by reading the characters correctly and converting them to the correct Unicode codepoints?"

So how do I configure Logstash to use UTF-8, so that the characters are shown in the right way in kibana?

I would recommend asking this question in the Logstash forum.

Okay, please close this one