Drupal fragile. It is touched and damaged

Dear Drupal friends.

2 months ago I installed Drupal and it has been 2 months lost. I have not advanced anything.
the current configuration is that of the first day.
Every time I try a change it is damaged. Every time I try to install a new theme, it gets damaged. The themes used, say they are compatible with Drupal 8.4.4.

The front of the page, shows the following:

The website encountered an unexpected error. Try it again later </br></br><em class="placeholder">InvalidArgumentException</em>: Field  is unknown. in <em class="placeholder">DrupalCoreEntityContentEntityBase-&gt;getTranslatedField()</em> (line <em class="placeholder">509</em> of <em class="placeholder">core/lib/Drupal/Core/Entity/ContentEntityBase.php</em>).

Again I have to restore the backup, again and again.

Why can not I install the themes? neither by file, nor by composer



Drupal version: 

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