duplicate pages

Good afternoon. Please help me with the problem. When checking the status of the site on the serpstat.com service appears the problem of duplicate titles. Example page https://gril.kiev.ua/produktsiia/poverkhnia-dlia-smazhennia.html and https://gril.kiev.ua/produktsiia/poverkhnia-dlia-smazhennia?format=html. It turns out that it is scanned a duplicate page. How to get rid of it?
And one more problem, when analyzing the site comes out the error " not specified encoding". This error applies to all pages of the site. Although when viewing the code of the page, you can see that the parameter is specified. What can be done with this.
Thank you in advance for your help.

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