Changes made is not reflected when running bench build

My git branch is showing as develop, I didnt given bench start but it is started automatically when given bench update and bench build also not works (Ie.changes made is not reflected when running bench build)

Did you setup production?
Type sudo supervisorctl status , what do you get?

frappe-bench-redis:frappe-bench-redis-cache RUNNING    pid 2237, uptime 5:37:09
frappe-bench-redis:frappe-bench-redis-queue RUNNING    pid 2236, uptime 5:37:09
frappe-bench-redis:frappe-bench-redis-socketio RUNNING    pid 2238, uptime 5:37:09
frappe-bench-web:frappe-bench-frappe-web RUNNING    pid 2234, uptime 5:37:09
frappe-bench-web:frappe-bench-node-socketio RUNNING    pid 2235, uptime 5:37:09
frappe-bench-workers:frappe-bench-frappe-default-worker-0 RUNNING    pid 2230, uptime 5:37:09
frappe-bench-workers:frappe-bench-frappe-long-worker-0 RUNNING    pid 2232, uptime 5:37:09
frappe-bench-workers:frappe-bench-frappe-schedule RUNNING    pid 2231, uptime 5:37:09
frappe-bench-workers:frappe-bench-frappe-short-worker-0 RUNNING    pid 2233, uptime 5:37:09

Yep, you have somehow setup production, which is why your ERPNext is starting without running bench start, along with that your changes are not being seen instantly as your site is being served via nginx. Run the below commands in order to stop production mode and go back to development mode.

cd frappe-bench
rm config/supervisor.conf
rm config/nginx.conf
sudo service nginx stop
sudo service supervisord stop
bench setup procfile
bench start