According to the Polish law, a standard working week is 40 hours within 5 working days, which amounts to 8 hours on average per day and is considered a full-time employment in most workplaces. Moreover, there is a set of obligatory days off, which in 2018 amount to 13 days.
Breaks from work are obligatory if an employee works for at least six hours a day. If this condition is not fulfilled and you work for a shorter period of time, breaks do not apply.
How long should it last? The standard break is 15 minutes for every day you work more than 6 hours and this time is counted as working time and you get paid for it. The law also allows to introduce a 60-minute break, but this longer lunch time is not part of your working time and you will not be paid for it, which means you will in fact spend one hour longer in the office.
Flexible working hours
More and more often employees in Poland are offered flexible working hours, especially if they are using civil or specific-task contracts. You can work in different hours in specific days and for a different amount of time, provided you discuss it with your boss. You can also ask for home office or spend more time at work Monday-Thursday to start your weekend earlier! In this day and age all is possible.
When you are asked to work more than you agreed in your contract, your extra work should be compensated either financially or as time in lieu. If you work part-time, your contract should determine what amount of overtime entitles you to get an overtime bonus. Sometimes your contract may already specify that a certain amount of overtime may be required and your salary includes this forecast. In such cases, compensation will not apply.
You can refuse to work overtime, but please bear in mind that the employer has a full right to ask you to stay longer, e.g. if there is an emergency requiring your assistance, for instance in saving human life or company property. It is illegal to ask a pregnant woman to do overtime in Poland.
Your further questions regarding these matters can be answered by the Polish labour code in English.