wp-content error

when I’m going to install a plugin

Try installing plugins manually: https://codex.www.ads-software.com/Managing_Plugins#Manual_Plugin_Installation

or even put some product in my virtual store

Are you using woocommerce?
If so, I recommend asking at https://www.ads-software.com/support/plugin/woocommerce so the plugin’s developers and support community can help you with this.