I was able to debug this issue while moving forward i am facing another issue.
when i launched piwik Ui on browser, it gives me error for mbstring ext and always_populate_raw_post_data=-1.
I have checked my piwik ext folder and mbstring is present in it and also i have edited php.ini file to make post data regarding config change, still piwik is showing same error on console even after restarting webservers.
What do you mean by checking the piwik ext folder? It depends on your PHP setup if mbstring is available. Maybe check the phpinfo()-page.
Make sure you have edited the correct php.ini file (the one corresponding to the php version you are now using). Otherwise phpinfo() should also show you if you have changed it correctly.