Edit: Csontzuzo has made a 100% walkthrough video (see his steam guide) and mentions the timestamps of the two relevant parts which is very helpful.

Compared to watching a video of the game, this guide contains only very slight spoilers, except for maybe the fact that there are two relevant parts which is a bit of a spoiler in itself.

The "visions" are the two sequences where you describe how the respective events took place, choosing from 3 options of what happened between the involved persons.

The first sequence comes after you deduct the time of Mark's death, and the correct sequence is:
select the red option (Mark standing at the doorway to the beach),
select the violet option (Mark and someone else sitting at the fireplace)
select the yellow option

The second sequence comes after you find the murder weapon (shortly after the circular marble labyrinth game) and is triggered when you speak to your colleague after he asks you "what did you find?" in a muffled voice because he is some distance away.

select the yellow option
select the red option
select the violet option
select the red option

Even with selecting wrong options there is no penalty except the time you spent on the misclick, so it's pretty doable if you don't take too much time to read the texts.

It can make sense to backup your savegame before a sequence, especially the 2nd one, just to make sure, because if you take more than 40 seconds for both of them combined, you would have to replay the whole game if you didn't backup any savegame. It is in Steam\userdata\youruserid\895420. I didn't have to do that so if anyone finds a problem with replacing the savegame, let me know and I might adjust this part of the guide.