https://www.duolingo.com/skill/pl/Food-1 part about meals explains a lot
Obiad is the main meal of the day, usually eaten around midday (12AM to 4PM). It is usually translated as lunch (because of the time of the day when it is eaten), sometimes as dinner (since it is the main meal which is often eaten socially – with family members, in a restaurant etc.)
Kolacja is a medium-sized evening meal, usually eaten between 6PM and 9PM. Again, since the conventions for naming a meal of this kind in English vary, it can be translated in two ways: as dinner or supper.
Yes, and often people refer to the middle meal as 'dinner' in northern England'. So breakfast / dinner / tea is the sequence. If you are lucky you may also eat supper before you go to bed.
A common expression for female helpers in school canteens is ''school dinner ladies". I think this expression is also used in the south even though they use 'dinner' to mean an evening meal outside of school.