how can you remove a echo from your recordings on audacity?

Short answer: You can’t.

The problem is that if you have, for example a voice recording, and it has an echo, the computer has no way to know what is “direct” voice and what is “echo”.

Longer answer:

There are a couple of advanced AI based solutions to the problem that are being developed, but are not (yet) available in Audacity.
(The other best known example is “nvidia RTX Voice”, but that requires specific nvidia hardware)