I started using Prestashop before 2 3 daysso I’m a total beginner, but I've got some questions.
1.i want to change button name but when i am done changes in blockuser.tpl and nothing is change i am removing cache also but no output.
You are changing core file of module.
There must be tpl file inside your theme folder. Change file on below mentioned path;
themes\{YOUR_THEME}\modules\blockuserinfo\blockuserinfo.tpl
Do your changes and clear cache and then check.