If the page crashes please enable Joomla debug mode and error reporting to see what the problem is and where it occurs

https://www.jevents.net/discussions/new-issue-after-installation is the same issue, please Geraint response in this post.
in the post "new Issue after installation" i reported the debuging errors.

that are:
Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 516096 bytes) in /home/aragonar/public_html/portal/libraries/joomla/database/driver/mysqli.php on line 894

this is the error, that happens when i add an event in the calendar. the site goes down.

And when i delete or disable the event in the backend of jevents it shows this error
-> Notice: Undefined variable: linkprevious in /home/aragonar/public_html/portal/modules/mod_jevents_cal/tmpl/ext/calendar.php on line 188

The site still working after deleted but if i try to add an event it crashes again.

I am wondering what sort of event you are adding - nothing should be using134MB of memory!

Can you add a very simple, non-repeating event in the backend of the site?

You can ignore the php notice in the calendar - it won't affect the output, its a notice to developers. It will be resolved in the next release

If you are able to give me login details on the private site details tab below we may be able to figure out what is happening