Two ongoing application processes—may I ask for more information?

Hello & Good Morning everyone,

I (f/25) currently have 2 positions "in prospect"

The first interview at Company X was the most appealing to me so far and is my favorite. Here's the status: We only have a second interview on Friday, and unfortunately, I don't get much more information from their message:

"We concluded our interviews yesterday. We are pleased to inform you that we would like to invite you to a further interview in our office."

Now yesterday I went to another interview at Company Y.
I can or should let you know by tomorrow (Monday) whether and under what conditions I would like to start there.

Now my problem is that I would rather start at Company X and the date is too far in the future considering my deadline tomorrow. I would like to contact Company X and ask how I should classify the current status and what the upcoming interview should be about, since I have another job offer that they are waiting for a response to, but they are my absolute favorites, etc.

(Company X is quite friendly and small—just 7-8 employees, so no major hassle with HR, hiring tests, etc.)

Theoretically, Company Y could possibly wait until Friday. Unfortunately, I can't predict that, or I could buy a little more time due to the upcoming salary negotiations.

Which path is better? What's the best way to proceed?
I can't imagine that Company X would be put off if I asked them about it – provided they were clearly my favorite.

I welcome comments from people who already have more professional experience than I do :)!