can't install the template

Hello. While installing the template the following text appears on the blank screen and the installation breaks.
Here is the text:
Warning: POST Content-Length of 61481600 bytes exceeds the limit of 8388608 bytes in Unknown on line 0
Error displaying the error page: Application Instantiation Error: Failed to start the session because headers have already been sent by "" at line 0.

Could you help me with this? What's wrong?

Could you please change value on php.ini file like below: