The most difficult part of the interview, as stated, is the dictation test, where they will have you listen to an audio recording and verbally dictate what you hear to a program on the computer that captures and types what you say.
If you are looking for a job here, practice dictating beforehand. Turn on the news on the radio or a Ted lecture or anything with someone speaking. Then verbally copy what they say, enunciating as clearly as possible, and also as monotone as possible. If you sound like a robot, that's good and makes it so the computer can recognize what you say better since computers aren't so great at recognizing tone of voice and accents. Practice dictating and getting the job will be a breeze.
You have to come up with some suggestions. Then the interviewer will give you two options and a budget to exercise these options. You have to justify your selection based on the maximum benefit achieved from the two options.