Solr 5 incompatible schema.xml An error kept showing after installing Search API for solr and after creating a server on drupal. (Solr 5.x)

You are using an incompatible schema.xml configuration file. Please follow the instructions in the handbook for setting up Solr.

Already copied alll configuration files from drupal module into:
/opt/solr/server/solr/my-core/conf

what else to check?
On Centos systems Solr assumes your cores will be stored in /var/solr/data/[core-name].

So if your core is named my-core, Solr might already have created the folder /var/solr/data/my-core for you. Simply place the conf directory in that folder, overwriting anything that might already be in conf.
No need to touch any of the other files.