Welcome back to the Wefugees Community and thank you for reaching out to us again.
Unfortunately, there is no guarantee that someone gets a residence permit because of a job. It is highly dependent on the individual case. It might make sense to discuss the details with an expert in a migration counselling office or with one of the MBE-advisors, who are also active on this platform and offer a private counselling via their App. In general, completing an "Ausbildung" (vocational training programme) is very important in Germany if someone wants to to qualified and better paid work in the long-run. I would always recommend to opt for the Ausbildung instead of a "normal" job if there is a choice. Also from your last question I did not get yet, what kind of residence permit your son holds. If its a so-called Ausbildungsduldung, he will have time for 6 months to get a new contract with another employer for his Ausbildung. If I remember correctly, he completed two years already, right? If that is the case, he should really not waste that time and try to finish it with another employer.
I hope this helps and please get back to us with any further questions.
All the best,