Well, that's certainly a nicer interpretation than that grandpa simply has Alzheimer's.
This is Genitive Case, correct? So do all feminine nouns' endings change from -a to -y? What happens with masculine and neuter nouns with Genitive?
It is safe to say that rules for "all" anything in Polish language are rare.
Feminine nouns end in singular genitive with -i or -y. That is also true for -a ending masculine nouns.
you can take a look on this table https://pl.wiktionary.org/wiki/Aneks:Język_polski_-_deklinacja.
masculine nouns end with -a, -u, neuter nouns end with -a
Also neuter and feminine nouns often have singular genitive=plural nominative. (Lampy)
The words for 'to buy' and 'to seek' are similar in Polish and Dutch. I'm assuming there's etymology there rather than it just being a coincidence.
It is very common, at least in American English, to say that you are "looking for" something,when you are shopping around until you find the one that you had in mind or one that you like, and if you don't find one that you like, you might not buy one at all.
Does Polish have different words for "to seek" and "to look for"? I wrote "my grandfather seeks a lamp" and it was not accepted.
No. Sometimes we forget to add options with 'seek', it's not the first word that comes to a non-native's mind. Added now.