Plugin is generating errors

Hi

Whenever i activate the plugin
The plugin generated 2428 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

Wordpress 4.8
Php 7.0 (it actually produces even more – 2999 – unexpected characters under php 5.6

Could you fix that ?

Thanks