I took my fourth with my sponsor. It took about six hours on a saturday. The next day I took the fifth. I was incapable of doing a fourth step on my own because I lacked the mental capacity. I didnt understand the words and had a lot of discussionn about the meaning of words and how they applied to me. I still have my fourth. It looks like it was written by a child, and it was! But it was enought to do the job, which was to get an honest appraisal of myself, especially those things that harmed me and others. It taught me the principle of inventory.
If you have a back to basiscs group in your area you could try that to get through the steps in a more time efficient fashion. The fourth step is taken with the help of a sponsor or sharing partner who does the writing for you. It takes 2 or 3 hours, and you will understand the principle.
The steps are never completed as such. They are a set of principles we learn and continue to practice as best we can on a daily basis. The fourth step is the first step requiring real action on our part. So many get hung up there, perhaps because they have heard it is difficult or frightening. It is neither if you can find the right help. And it is vital to get past it if you want permanent and happy recovery.