Warning: file_put_contents(sites/default/files/php/twig/5ec7c76bcb94c_menu.html.twig_ms5R93s-wUkYaDlrCxbz7FVzS/.htaccess): failed to open stream:

Those kind of messages are a folder permission problem at the most of time. And may be it's the case of your Drupal installation. So I invite to verify the owner of "files" directory:

chown -R :www-data files

Then setting the proper permission on the Files directory:

chmod g+ws files

Fixing the permissions of pre-existing files in the Files directory:

cd files && find . -type d -exec chmod g+ws {} \ && find . -type f -exec chmod 664 {} \;

As recommended by Chris Toler.

And be careful because may be you are using a Dockerfile that force Nginx to use another user then www-data or may be you are using a shared volume for "files" directory as a cloud webapp. In that case you need to verify permissions on volumes at the host machine or using the Cloud UI to find the right permissions for your volumes. For further reading you can take a look at this Drupal topic.