How can I get a channel ID from YouTube?

You can get the channel ID with the username (in your case "klauskkpm") using the filter "forUsername", like this:

https://www.googleapis.com/youtube/v3/channels?key={YOUR_API_KEY}&forUsername=klauskkpm&part=id

More info here: https://developers.google.com/youtube/v3/docs/channels/list

An easy answer is, your YouTube Channel ID is UC + {YOUR_ACCOUNT_ID}. To be sure of your YouTube Channel ID or your YouTube account ID, access the advanced settings at your settings page

And if you want to know the YouTube Channel ID for any channel, you could use the solution @mjlescano gave.

https://www.googleapis.com/youtube/v3/channels?key={YOUR_API_KEY}&forUsername={USER_NAME}&part=id

If this could be of any help, some user marked it was solved in another topic right here.

This website finds a YouTube Channel ID from its URL:

https://commentpicker.com/youtube-channel-id.php

To obtain the channel id you can view the source code of the channel page and find either data-channel-external-id="UCjXfkj5iapKHJrhYfAF9ZGg" or "externalId":"UCjXfkj5iapKHJrhYfAF9ZGg".

UCjXfkj5iapKHJrhYfAF9ZGg will be the channel ID you are looking for.