What website or forum to use as security professionl

I like SC Media for an overview

https://www.scmagazine.com

CISA (part of US DHS) www.us-cert.gov
Krebs on Security - www.krebsonsecurity.com - This gives deeper explanations.
CERT CC - https://www.kb.cert.org/vuls/

Go to CVE Details' Product or Vendor pages. There is "Vulnerability Feeds & Widgets" link there.

https://www.cvedetails.com/

product centric vulnerabilities

https://www.zerodayinitiative.com/advisories/published/

Zero day database

https://www.zero-day.cz/database/

CERT Alerts

https://www.us-cert.gov/ncas/alerts

SANS Threat feeds and more

https://isc.sans.edu/threatfeed.html

You can also subscribe to this mailing list "bugtraq@securityfocus.com". A lot of vendors and researchers keep updating about new vulnerabilities.

in addition
https://www.rsa.com/
https://www.sans.org/
https://infosec-conferences.com/conferences-top-ten-must-go-to/
http://www.securitybsides.com/w/page/12194156/FrontPage/
https://www.theregister.co.uk/
https://www.bleepingcomputer.com/news/security/

and some more:
from https://onlinedegrees.sandiego.edu/top-cyber-security-blogs-websites/
1. Daniel Miessler
2. Graham Cluley
3. IT Security Guru
4. Security Weekly
5. The Hacker News
6. Infosecurity Magazine
7. CSO Online
8. The State of Security – Tripwire
9. Troy Hunt
10.  The Last Watchdog
11. Schneier on Security
12. The Akamai Blog
13. Krebs on Security
14. Naked Security
15. TaoSecurity  
16. Dark Reading
17. PC World
18. Wired
19. CIO
20. CNET
21. We Live Security
22. Signal Magazine
23. ThreatPost
24. Computerworld

From (with some overlap) https://securityscorecard.com/blog/top-10-information-security-websites-to-follow
1. Brian Krebs
2. Wombat Security
3.  Errata Security
4. Kaspersky Labs
5. Security Bloggers Network
6. Sophos
7. Paul’s Security Weekly
8. Akamai
9. The Security Ledger
10. Graham Cluley

Security blogs and social media

 Examples include:
• Fortinet Blog: http://blog.fortinet.com
• Naked Security: http://nakedsecurity.sophos.com
• Security Blogger's Network: www.securitybloggersnetwork.com
• Network Security Blog: www.mckeay.net
• Securosis Blog: https://securosis.com/blog
• Uncommon Sense Security: http://blog.uncommonsensesecurity.com
• Paul's Security Weekly: http://securityweekly.com
• TaoSecurity: http://taosecurity.blogspot.com



Security mailing lists, newsgroups, and newsfeeds

 Examples include:
• CERT-UK cybersecurity alerts: https://www.cert.gov.uk/resources/alerts/
• The information security breaches survey, carried out annually to assess breaches in UK-based organizations: https://www.gov.uk/government/publications
• Usenet newsgroups such as alt.security, comp.risks, comp.security.announce, and comp.virus
• Internet Storm Center Handlers Diary: https://isc.sans.edu