Hi,
Thank you for the details.
Okay, I logged in and tried a few searches. I noticed that there is a difference in search results when typing “3step” or “3 step”: https://i.imgur.com/6m3VVS6.png
The phrase “3step” gives less matches, beuse the word “3step” only appears on very few products. In most cases the words “3” or “step” are present.
I noticed you also have synonyms as a possible resoltuion, but that is not going to work here either, as synonyms only work as single keywords, and you rather want “3step” replaced with “3 step”.
Less strict logic won’t help either, because the word “3step” will never match “3” and “step” in any scenario.
I believe this tutorial is what you are looking for. You rather want to replace the “3step” in the search input to “3 step”:
$replace = array(
'3step' => '3 step'
);