Four weeks is enough if you spend it in the right order. The most common failure is not doing too little - it is doing a month of untimed practice on the topics you already enjoy.
Week 1 - diagnose
Do not study yet. Find out where you actually stand.
Take a timed mental-math test cold, and a set of 20 mixed probability questions with a clock running. Write down two numbers: how many you got right, and how many you got right in time. The gap between those is usually the real problem.
Then read the process for the specific format you are facing. A timed arithmetic screen and a research interview need almost disjoint preparation, and generic prep serves neither.
Week 2 - the screens
Whatever is between you and a human is the priority, because everything else is wasted if you do not pass it.
For most trading pipelines that means arithmetic speed and sequences. Twenty minutes a day, every day, beats three hours on a Sunday - this is a motor skill and it consolidates with sleep.
Alongside it, start expected value and probability fundamentals. Aim for fluency on the standard forms rather than coverage of exotic ones.
Week 3 - interview shape
Now work the way you will be asked.
Practise out loud. Say what you are doing while you do it, even alone - it feels absurd and it is the single highest-return habit for these interviews, because most processes explicitly mark communication. See thinking out loud.
Add market-making games if you are interviewing for a trading seat, and brainteasers for the archetypes you have not seen.
Week 4 - calibrate and stop
Do full timed sets under realistic conditions. You are checking pace and nerve, not learning.
In the last three days, stop adding material. Re-read the problems you got wrong, sleep properly, and go in rested. A tired candidate makes arithmetic errors, and arithmetic errors are the thing these processes actually filter on.
If you have less than four weeks
Cut in this order: exotic topics first, then breadth, then depth on your weakest area. Never cut the timed practice or the sleep.