Very thanks to the 1st answer by @Martin v. Löwis.
Yes, that worked great. In my case, using --use-fuzzy switch was very useful.
In my case, the content of .po file lines (not working) was something like below. All translated lines were working except this.
#: ui/templates/theme/html/ltr/vertical-menu-template-nav-dark/login.html:58
#, fuzzy
#| msgid "Already a registered user (Login)"
msgid "Not a registered user (Create account)"
msgstr "Уже зарегистрированный пользователь (логин)"
Here is output of my terminal after executing django-admin compilemessages --use-fuzzy.
(venv3.6.7) Rishikeshs-MacBook-Air:src hygull$ django-admin compilemessages --use-fuzzy
processing file django.po in /Users/hygull/Projects/Python36/Django/Others/AMCProj/amc/src/locale/hi/LC_MESSAGES
processing file django.po in /Users/hygull/Projects/Python36/Django/Others/AMCProj/amc/src/locale/ru/LC_MESSAGES
processing file django.po in /Users/hygull/Projects/Python36/Django/Others/AMCProj/amc/src/locale/en/LC_MESSAGES
Finally, after running the command, just restart the server i.e. python manage.py runserver.