Can I work legally on the basis of the stamp that was placed in my passport, while I wait for my decision on granting a residence permit?

The stamp does not entitle you to take up legal employment in Poland. In order to work legally, you need to fulfil one of the following conditions:

1. On the day of the submission of your application, you were a holder of a valid document entitling you to work legally (a valid declaration on entrusting work to a foreigner or a work permit) and that document is still valid;
2. You applied for a new residence and work permit, and the grounds of your employment have not changed since your previous permit was issued, i.e. you still occupy the same job position in the same company (continuation of employment);
3. On the day of your application, you held a valid type A work permit and you applied for a residence and work permit on the basis of employment in the same company for which the work permit was issued (on condition that your position and type of employment contract have not changed) - continuation of employment;
4. On the day of your application, you held a valid declaration on entrusting work to a foreigner, based on employment contract (excluding civil law contracts), on the basis of which you had been working for the three months preceding the application, and you occupy the same position in the same company for which the declaration was issued – continuation of employment;
5. On the day of your application, you held a valid  declaration on entrusting work to a foreigner issued by District Employment Agency, based on employment contract (excluding civil law contracts), on the basis of which you had been working for at least three full months, your application contained no formal errors and you received a stamp in your passport – certifying that you applied for a residence permit – you can legally work for as long as the declaration is valid, unless your employer applies for a type A work permit (not earlier than after full three months of your work on the basis of the declaration, but before it expires). Additionally, your job position, the employer and the type of contract must remain the same as those indicated in the declaration of work entrustment issued by District Employment Agency;
6. You are exempted from the necessity to obtain o work permit, for instance: you are a graduate of Polish secondary schools, or have completed full time studies (tertiary education), or full-time doctoral studies at Polish universities and scientific and research institutions.