I have a little question

Old stand-alone CD-players don’t play mp3-format audio files.
Here’s how to make a CD which is playable on stand-alone CD players …
https://manual.audacityteam.org/man/burning_music_files_to_a_cd.html

Presumably you transferred the files to CD simply by copying them. Most CD players will not recognise the windows file format so you require software which will take your files and write them in the standard format for an audio CD. For example there is an optional component for Foobar 2000 called audio CD writer. Foobar2K is free software although not open source like Audacity.

MP3 is a compressed format (where some of the audio information is thrown away) mainly for use on small portable playback devices - MP3 - Wikipedia

For making CD’s you need WAV files - and Trebor’s instructions

WC

I presume yo mean 2.0.5 ?

If so that is a very old version - the latest release is 2.2.2 and we’ve fixed a lot of bugs and added good new features since 2.0.5.

You can get the latest release from here: Audacity ® | Download for Windows

This page in the Audacity Wiki will shoiw you the changes since 2.0.5: Missing features - Audacity Support

WC