Hi!
Okay, I think I understand better now. I hope you don’t mind, but I have made the following adjustments to the search, based on your requirements:
1. I have disabled both categories and attachments as results, since the downloads are a separate post type, and I believe you don’t really want the categories as results. You can still re-enable these, I am just guessing.
2. I turned off the post type ordering logic, since in the example case the first result is a post and the second is a download post type, so it will hurt the relevance matching.
3. I also switched the search logic like so: https://i.imgur.com/yks7U2V.png
This will give more strict matches first, then less strict will follow.
4. I also turned off polylang compatibility, as I don’t see translations for the downloads yet. In that case, it is possible, that some elements might not be properly assigned to languages, and can be excluded: https://i.imgur.com/hA0pYDG.png
Once you got all the translations ready, you can turn it on again.
Now, doing a test search for ‘Monkey Puzzle’ does return much more relevant matches, and it even returns the first two results as you expected: https://i.imgur.com/3iJyRIv.png
I hope this helps!