SSL error when installing application

Please delete everything above when creating your topic and provide the following:

Nextcloud version (eg, 12.0.2): 13.0.0
Operating system and version (eg, Ubuntu 17.04): Ubuntu 16.04.3 LTS
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.18 (Ubuntu)
PHP version (eg, 7.1): PHP 7.0.25

The issue you are facing:
I have a paid certificate and I uploaded it to NextCloud. There is no problem with the certificate tests.But when I try to install the application I get the following error.
"Curl error 60 : SSL certificate problem:self signed certificate in certificate chain.

I upgraded to version 13, but there was a problem in 12.

The output of your Nextcloud log in Admin > Logging:

rror	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T21:17:11+0300
Error	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T21:16:46+0300
Error	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T20:58:49+0300
Error	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T20:56:01+0300
Error	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T20:48:39+0300
Error	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T20:43:17+0300
Error	core	cURL error 60: SSL certificate problem: self signed certificate in certificate chain	2018-02-12T20:22:10+0300
Info	updater	\OC\Updater::resetLogLevel: Reset log level to Warning(2)	2018-02-12T20:21:05+0300
Info	updater	\OC\Updater::maintenanceDisabled: Turned off maintenance mode	2018-02-12T20:21:05+0300
Info	updater	\OC\Updater::updateEnd: Update successful	2018-02-12T20:21:05+0300
Info	updater	\OC\Updater::finishedCheckCodeIntegrity: Finished code integrity check	2018-02-12T20:21:05+0300
Info	updater	\OC\Updater::startCheckCodeIntegrity: Starting code integrity check...	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Add log rotate job	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Rename folder with user specific keys	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Repair invalid paths in file cache	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Install new core bundle components	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Repair language codes	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: No mounts updated	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Fix potential broken mount points	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Add preview cleanup background jobs	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: Repair step already executed	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Add move avatar background job	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: .step file moved to .step-previous-update	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: .step-previous-update removed	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: .step file exists	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Move .step file of updater to backup location	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Remove shares of a users root folder	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Repair invalid shares	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: 0 tags with no entries have been removed.	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: 0 tag entries for deleted tags have been removed.	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: 0 tags for delete files have been removed.	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: 0 tags of deleted users have been removed.	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Clean tags and favorites	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Repair mime types	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::info: Repair info: All tables already have the correct collation -> nothing to do	2018-02-12T20:20:26+0300
Info	updater	\OC\Repair::step: Repair step: Repair MySQL collation	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreApp: Checked for update of app "workflowengine" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreAppBefore: Checking for update of app "workflowengine" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreApp: Checked for update of app "updatenotification" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreAppBefore: Checking for update of app "updatenotification" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreApp: Checked for update of app "twofactor_backupcodes" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreAppBefore: Checking for update of app "twofactor_backupcodes" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreApp: Checked for update of app "theming" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreAppBefore: Checking for update of app "theming" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreApp: Checked for update of app "systemtags" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreAppBefore: Checking for update of app "systemtags" in appstore	2018-02-12T20:20:26+0300
Info	updater	\OC\Updater::checkAppStoreApp: Checked for update of app "survey_client" in appstore	2018-02-12T20:20:26+0300

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

<?php
$CONFIG = array (
  'instanceid' => 'ocvpvvz910h0',
  'passwordsalt' => 'rc+ARYVqGnuokmPtcK151YZ3/7QAUz',
  'secret' => 'xvxl6XTE965hmTieAS3yAst1/SfmX8nlT6SvDt2U5hGINPMb',
  'trusted_domains' =>
  array (
    0 => 'bulut.pendik.bel.tr',
  ),
  'datadirectory' => '/var/www/nextcloud/data',
  'overwrite.cli.url' => 'https://bulut.pendik.bel.tr',
  'dbtype' => 'mysql',
  'version' => '13.0.0.14',
  'dbname' => '######',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => '####',
  'dbpassword' => '######',
  'installed' => true,
  'mail_smtpmode' => 'smtp',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpsecure' => 'tls',
  'mail_from_address' => '#####',
  'mail_domain' => '#####',
  'mail_smtpauth' => 1,
  'mail_smtphost' => '#####',
  'mail_smtpport' => '#####',
  'mail_smtpname' => '#####',
  'mail_smtppassword' => '#####',
  'updater.secret' => '#####',
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 2,
);

Can you provide your Apache config files, how you implemented the certificates there?