MacBook Pro - macOS Mojave - system space increased rapidly

Hi guys,

I have a big problem. I use a mac book pro (early 2015) with the newest OS. Since a few days, I always get an alert, that my disk space is kind of full. Usually, I used 45-50gb from my 125gb SSD, now my system should take over 75gb data. I dunno why and use google. A lot of other people had the same issue so I tried a few things to solve the problem or find the file. But I cant.

I have never used time machine and it's not activated. But last week, unfortunately, my yogurt got on my macbook, I brought it to a service, they did an alcohol bath and everything worked now again. They also back up my data on my external hdd. Is this maybe the result? Maybe there is still a backup file somewhere on the system? It this possible?

what I have done:

1. I run OmniDiskSweeper but all look "fine". But I read that ODS isn't working in mojave in case of permission stuff?

2.

save restart > showed same results

3.

made all hidden items visible and searched in the library if I can find a big sized file > was nothing

4.

I put in my terminal the following command: sudo du -hcx -d 1 /

All entries make sense but on two I dunno what they mean.

43G /
43G total

Does anyone have an idea?

I hope someone can help me out 😟