RSS feed only shows title

[Blubberland]

My RSS Reader (FreshRSS) only shows the title of the posts.

Because I have no idea what I'm doing I put it into a RSS validator.

This feed does not validate.
line 1, column 564: Invalid email address: Andreas Kling (5 occurrences) [help]
... uncement</category><author>Andreas Kling</author></item><item><title>Lad ...
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In addition, interoperability with the widest range of feed readers could be improved by implementing the following recommendations.
line 1, column 168: descriptionshould not contain HTML: & [help]

... a brand-new browser &amp; web engine</description><link>https://lady ...
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line 1, column 2102: Missing atom:link with rel="self" [help]

... ><author>Chris Wanstrath</author></item></channel></rss>
---------------------------------------------------------------------^

I'm not sure if the shown issues there, are related to my problem (they don't look like they would), but I thought I might as well report it.