Here are some links for some popular Telegram groups strictly for competitive programming:
Group 1 : This group has more than 2500 competitive programmers.
Group 2: This group has more than 1600 competitive programmers.
Group 3: This group has more than 2400 competitive programmers.
Feel free to join all these groups and enrich you knowledge.
Some of the group members are Grandmaster. They are very helpful and help you any time in any questions.
BEFORE DOWN VOTE PLEASE ATLEAST CHECK THOSE GROUPS