First of all....Welcome to the Cisco Learning Network!
Congratulations on passing your 210-250 exam. Great achievement!
Also very good insights you provide regarding 210-250 study materials and your exam experience.
Thank you for sharing them with us.
Regarding advice for the 210-255 exam, you might want to check the valuable feedback on study material and exam advice from Phoenix and Shane, great community members here at the Cisco Learning Network. You can check there great posts on study materials and exam experience on the 210-255 at the following links:
Also dont forget the valuable information available here at the Cisco Learning Network. You can check the following links with Exam Topics and Study Material:
Additionally for official study material, you can check Cisco Press at the following link:
If you would like to consider an E-learning option for the 210-255 exam, which includes a FREE trial version. You can check the following link:
I wish you all the best in your Cisco CCNA Cyber Ops certification studies.