If the translation includes "your + beer", why isn't "your + beer" included in the original sentences?
Czech does not use possessive pronouns the same way as english. The verb already shows the ownership. When we say for example Máš v kapse klíč. (You have a key in your pocket) - MÁŠ - shows that we speak about you. V KAPSE -the pocket is on your clothes so it can be only yours and there is no need to emphasize it with a possesive pronoun. KLÍČ- when there is no possesive pronoun then the key belongs to you. When there is a possesive pronoun then the key belongs to that person according to the pronoun.
Does it work in other side too? That when translating from Czech to English we need to add possessive pronoun. So "You have a fly in the beer" - is not a correct translation? Or it is acceptable too?
Neither of the following "translations" is idiomatic English:
1. You have a fly in a beer.
2. You have a fly in the beer.
On the other hand, you do not always need the personal possessive pronoun in English. All the following are correct,with different meanings:
1. You have a beer in the fridge.
2. You have a beer in a fridge.
3. You have a beer in your fridge.
What does it depend of, if a neutrum changes to -u or -e ending? Pivo - Pivu Slovo- Slove Can't be the thing with soft and hard letters from my understanding.