After submitting my application, I got a reply in around 3 days asking for a phone interview, after you pass this one, you got a coding challenge task that you should complete

Applied for job online from abroad for Berlin office. I read a few previous interview reviews which say the process was of average difficulty, so I was a bit surprised that I didn't make it, but I think they've made it more difficult recently with the hire of their new CTO last year and they've added an additional step (the CTO interview) to the hiring process. Steps: 1.) HR interview - fairly standard stuff 2.) Coding challenge - spent ~8hrs on it, but could have been closer to 6 had I focused 1st on a good algorithm first and would have saved me from rewriting it 3.) Technical interview - includes a coding question on an online/shared notepad 4.) Behavioural interview - with the CTO 5.) Feedback about process - this skype call was a pleasant surprise, and at least they tell you why they didn't want you and possibly what you can do to improve