I did it, oh my
For people who face the same problem i will left here the solution that i used

$ sudo apt install php-curl
$ sudo apt-get install curl libcurl3 libcurl3-dev;

$ sudo apt-get install php7.0-curl
$ sudo service apache2 restart

Curl is already installed. When i try to install, it get's me Unable to locate package
Opensource package is not available on Ubunty
This is also 500 eternal server error showing on /installation

Who told you mcrypt required, looks like php curl extension missing.

Please try to use following for ubuntu installation https://www.opensource-socialnetwork.org/wiki/view/3994/how-to-install-ossn-on-ubuntu-x64-using-command-line

mod_rewrite is on, mcrypt too

[Sat May 09 16:09:53.515231 2020] [:error] [pid 940] [client 188.65.246.231:48813] PHP Fatal error: Uncaught Error: Call to undefined function curl_
init() in /var/www/html/installation/libraries/ossn.install.php:218\nStack trace:\n#0 /var/www/html/installation/classes/OssnInstall.php(46): ossnin
stallationsimplecurl('http://35.193.1...')\n#1 /var/www/html/installation/pages/check.php(35): OssnInstallation::ismodrewrite()\n#2 /var/www/html
/installation/libraries/ossn.install.php(76): include('/var/www/html/i...')\n#3 /var/www/html/installation/libraries/ossn.install.php(141): ossninst
allationinclude('/var/www/html/i...')\n#4 /var/www/html/installation/index.php(32): ossninstallation_page()\n#5 {main}\n thrown in /var/www/html/i
nstallation/libraries/ossn.install.php on line 218

There's a problem
Standart GCP server ^ 16/04 Ubunty