That page was useful thanks! I heard all the sounds and I learnt how to pronunce lot of letters https://forvo.com/user/Zababa/pronounced-words/page-3/
well.... sorry, this might be longer. They sound the same.... sometimes.
Third grade of Czech schools is pure hell. Kids have to learn which letters can be followed by I, which by Y and which by either.
ž š č ř c j ď ť ň are always followed by I. always.
h ch k r d t n are always followed by Y (with very few exceptions that are foreign words keeping foreign spelling)
b f l m p s v z can be followed by either and you have to learn by heart words where Y is used and then apply I everywhere else.
Notice, that there is ď ť ň and d t n are once under i and once under y. The confusion you have comes from this group. d t n followed by i are pronounced as ď ť and ň even if they "hook" is not there. Actually the "hook" is never there because the i makes it "soft". For Czechs this is no biggie and does not represent a problem even for the third graders. They all get stuck on the b f l m p s v z.
I and Y sound the same post every other letter but D T and N.
Technically speaking, they can be masculine inanimate as well ("Stoly, ony jsou staré"; not sure whether this word order works in Czech, however), but usually an animate object is assumed in context of usage of adjective "old", that's why feminine.
But this information can be extracted only from the Czech sentence, not the English one.
Edit: s/masculine animate/masculine inanimate/, sorry for confusion.
I thought I had this clear but after reading this i need a summary so...
Putting to jsou aside for a bit. (I know to jsou is they are)
Ony jsou is only feminine??
Oni jsou is only masculine??
To jsou for not only Neuter. I thought only masc was Ony - Ony jsou dobri muzi only Fem was Ony jsou dobre zeny only neut would be To Jsou dobra auta and masc, fem and Neuter together would be ONY jsou dobri muzi, dobre zeny a dobra auta