How to solve 'failed to open stream' when executing bin/console?

Hello,

I have just installed vagrant for shopware like described here ‚shopwareLabs/shopware-platform-vagrant‘ on OSX.
I can do vagrant ssh. But when I execute ‚./bin/console‘ I got an error:

PHP Warning:  require(/home/vagrant/shopware-dev/bin/../vendor/autoload.php): failed to open stream: No such file or directory in /home/vagrant/shopware-dev/bin/console on line 20PHP Fatal error:  require(): Failed opening required '/home/vagrant/shopware-dev/bin/../vendor/autoload.php' (include_path='.:/usr/share/php') in /home/vagrant/shopware-dev/bin/console on line 20

It is because the vendor folder is not there. So I thought I have to execute ‚composer install‘.
So, when I do that I got this warning and error:

Warning from https://packagist.org: You are using an outdated version of Composer. Composer 2.0 is now available and you should upgrade. See https://getcomposer.org/2

In RemoteFilesystem.php line 305:

  Content-Length mismatch, received 244853 bytes out of the expected 291227

How can this be resolved?

I have tried to update composer, but I got this error:

Command "self-update" is not defined.