that means i can't travel to Schengen countries ? i think Poland is one of Schengen countries

A national visa (D) authorizes the residence:
- On Polish territory for the duration of the stay and the period of validity for which it was issued;
- And in addition to travel through the territory of other Schengen countries for three months in half year.

can i work as a part timer with this visa if not then i have to do 4 that

Also, a student who is a foreigner , can legally work in Poland without having official permission , provided that studying day and has a residence card . In another case ( for example, when studying wieczorowo ) to work legally should have a visa with the right to work. In such a situation, a student applying for a visa , instead of a permit shall submit a written statement of the employer of his intention to work in Poland . This applies to students :

a full-time studies pursued in Poland - in July, August and September ;

b taking professional internships implemented by organizations that are members of international associations of students ;

c who work in the framework of public employment services and their foreign partners , if necessary the foreigner work is confirmed by the competent authority of employment ;

d colleges who undertake apprenticeships ( within 6 months), under the regulations of study or curriculum, organized in the framework of an agreement between a foreign institution of higher education and the employer, registered with the labor office competent for the place of residence of the employer ;

e of higher education ( in the Member States of the European Union or the European Economic Area countries outside the European Union or of the Swiss Confederation ) who undertake apprenticeships under the regulations of study or curriculum, subject to referral to the practice of higher education .

if i got a part time job in Poland how much my Monthly income will be or with this can i work as part timer outside poland like Germany ect. is work permit required ?

I consider English as a main language.

§ 2. 1. Wizę krajową oznacza się symbolem "D".
10)"10" - gdy wiza jest wydawana w celu odbycia studiów pierwszego stopnia, studiów drugiego stopnia lub jednolitych studiów magisterskich albo studiów trzeciego stopnia;

As a native Pole i think American English is the "cleanest" one to understand.

I just don't understand why they allow no ZUS on those contracts.

If you teach (especially if you teach in-company), you are not under employer supervision.

You might be getting slightly confused with an umowa zlecenia,

Thank you, again, Harry. So, from that I assume the employer also pays the ZUS unless I have a company registered elsewhere in the EU in which case I don't pay ZUS.

a driver may not pass the right to drive on this car to another person( to a wife, a husband or just a friend.

what is the rule for Employment after post study work in Poland ?

I think outside Poland, your degrees will be given the respect they deserve mate!

One step at a time!!

Gap between the rich and poor widening? Not good for society if so, is it?

Amazon is just one example of this momentum. several thousand (admittedly ****) jobs for Wroclaw and Poznan, a direct result of the improved road infrastructure provided by the EU and an understanding of Polands economy as a current and future attraction.

A direct result of the strikes that hit Amazon in Germany. American companies hate unions and worker's councils. They'd rather close down a location than dealing with them.