Technical Interviews are hard, here are some practices to process them more easily:

Websites

• LeeCode - Highly recommend, questions are from real interviews and well written
• GlassDoor - You can look up a company that you are interviewing with and look at their previous interview questions.
• HackerRank - Questions are not always well worded but a lot of companies use HackerRank for their interviews.
  Books
• Cracking the Coding Interview - The bible of coding interviews. Solutions to questions can be found here.
• The Algorithm Design Manual
• Introduction to Algorithms

Videos