Hi Hooiin,
I hope you are well today and thank you for your questions.
Then i wanted to ask if it is allowed to change the footer line on the left “Copyright © 2016 “website”. Theme by Colorlib Powered by WordPress”
Yes it’s allowed 
and if how am I going to do that?
You can customize your footer copyrights text by using the solutions posted in the following replies.
https://colorlibsupport.com/t/custom-footer-text/#post-28247
https://colorlibsupport.com/t/how-to-center-text-in-footer/#post-28516
https://colorlibsupport.com/t/footer-copyright-customize/
https://colorlibsupport.com/t/footer-copyright-note-in-child-theme/
Best Regards,
Movin