A friend of mine (US citizen) in Berlin was just laid off after 9 days on the job. It was not performance-related, as the company is quite obviously struggling and let go of many people on the same day. In case the context is helpful, she's a UI/UX designer with 5+ years of experience working in San Francisco, CA.
She's been in Germany for 33 days and had a valid residence/working permit for 10 days prior to the layoff, ergo, she'd 'used up' 23 days of her tourist visa.
Edit: Based on an earlier post, h/t @Gala, at a minimum, she should be allowed to stay in Germany for the 67 days remaining on her tourist visa.
What we haven't been able to confirm, though, is whether the permit she was given allows her to stay in Germany for 3 years but without the right to work for another company unless otherwise granted (IOW, a situation where the work permit is tied to her previous employer only, but her residence permit remains valid unless explicitly revoked), OR whether both her working and residence permit expire in 2 weeks when she's officially no longer employed by the company that sponsored her.
The first page of the permit, which has work-related info, reads:
"Beschäftigung nicht gestattet mit Ausnahme der Tätigkeit als UX/UI Designer bei [redacted], 10*** Berlin bis zum 14.10.2018. Selbstständige Tätigkeit gestattet"
...which Google Translate renders to:
"Employment not permitted except for activity as a UX / UI Designer at [redacted] 10*** Berlin until 14.10.2018. Independent work permitted"
(Note: reads as though she's also allowed to freelance, which is good news because it's common in her field).
The second page of the permit, titled Aufenthaltstitel (Residence Permit), shows the Gültig Bis (Date of Expiry) as 14.11.18. The Art des Titels (type of permit) in this section is Aufenhaltserlaubnis (again, Residence Permit). There's no mention of her employer on this page.
An optimistic reading of these 2 pages is that while her working permit allows work only with her previous employer (and potentially, freelance work too), her residence permit is valid for 3 years regardless of her employment status, so she's at least free to remain in Germany during that time to try to find full-time work, at which point the new company would need to help her secure an updated work permit.