I don't understand why you use chłopca here instead of chłopci (or whatever the other word is)
"chłopiec" is the Nominative (dictionary form) form of "boy", "chłopcy" is plural Nominative.
"widzieć" (to see) takes Accusative, which for singular is "chłopca" (and for plural: "chłopców").
Thanks a lot for this input, but I was wondering, I usually referenced myself to the Wikipedia table of the cases, and they don't really indicate these endings, would you (or anybody else really) know of a complete table that includes all of the endings for all cases and genders ?
I found something like this: http://www.polskinawynos.com/wp-content/uploads/2014/08/rzeczownik-zestawienie-koc584cc3b3wek1.pdf
Accusative is the only case where it's important whether a masculine noun is animate or inanimate. "chłopiec" is animate, so the Accusative form will be identical to Genitive form. And yes, it mostly ends with -a.
No, because 'this' is not an article like 'a' or 'the', and so is not an omitted word. Given chłopca is a masculine noun I believe you would need 'to chłopca' to refer to 'this boy'
We do not have the, this= ten, ta,to is sometimes translated to the, also much more often used than that=tamten, tamta, tamto which is used only when referring to the other thing. Also to=this/that is used when separate, or as replacement to is and the gendered versions are used when they are before noun and easily translate to the.
But I think duo accepts both omitting the or translating it to ten/ta/to, but not adding "this" where there is no "to" in Polish.
Not "boys", plural, but "boy's", the possessive form of "boy". The Accusative and Genitive forms of "chłopiec" look the same, so the hints need to include the option for the possessive use of the Genitive form.