Please help me out on this matter and also tell me how to upload it to root directory?
This is a problem with the most recent version of PHP. You should generally not be showing deprecated warnings on your site, check your PHP configuration.
But to solve this issue, you can follow the instructions on this page. And it will be fixed in v1.7 final.
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April 20, 2021: Q2A 1.8.6 released!