i need some advise regarding storage of data
is it good to store data in files rather than storing into database? (eg data like comments or additional features of products that users advertise on our website.) will it help for speed optimization.

Of course!
Take for example simple search process to check how many people earn between 20k-25k. With file approach you need to read the file, temporary store it somewhere, close the file, you need to iterate trough to find results and then do what ever you want. Where in case of database you just write a query and check for results from DB.

thanks peter_budo
i've switched to DB storage