Welcome to the Wefugees Community and thank you for your question.
If you receive social benefits, including social benefits for asylum seekers (Asylbewerberleistungen), the respective authority will calculate exactly what you need to cover your monthly costs (the costs for your accomodation plus a fixed amount for your daily expenses which also depends on marital status, age etc.) and deducts your income from it. If you can not cover your costs according to this calculation, the authority (in your case Sozialamt) will jump in to cover the rest.
Additionally, there is a so-called "Freibetrag" on your work income. If I am not mistaken, 25% of your monthly gross income but max. 50% of that above mentioned fixed amount to cover you daily expenses/"Regelbedarf" (450 Euro --> 112,50 Euro) will be "untouched" and not deducted/taken into account.
I assume that you will not be able to survive with only 450 Euros per month and the Sozialamt will support you with the rent at least. I hope this was helpul and please don't hesitate to get back to us with any further questions.
All the best,