Hi Lorenzo and welcome back to the mysteries of the Czech language! I'll do my best to try and answer your intriguing questions.
Constructions with "aby"
"Chci, abys to věděl" is a correct translation of "I want you to know that". The word "aby" is a conjunction and means "so that, in order to". It is used here because that's how constructions like "I want something to happen" or "I want someone to do something" are created in Czech. Examples:
I want you to leave. - Chci, abys odešel / odešla.
I want him to leave. - Chci, aby odešel.
I want the weather to be nice. - Chci, aby bylo hezky.
I want us to be friends. - Chci, abychom byli přátelé.
I want you (plural) to be happy. - Chci, abyste byli šťastni.
I want them to stop talking. - Chci, aby přestali mluvit.
As you can see, the word "aby" changes based on the person it refers to. Here is the complete set:
abych - já
abys - ty (shortened from "aby jsi")
aby - on, ona, ono
abychom - my
abyste - vy (shortened from "aby jste")
aby - oni
The verb that is used in the sentence that begins with "aby" is always in the "past tense". It is not really past tense but rather the conditional form of the verb. If you look up conditionals (podmiňovací způsob) in your book, you will see that they are partially formed like the past tense.
The "aby" constructions always follow this pattern, no matter in what person or tense the verb in the first sentence is. Examples:
I will want you to read that = Budu chtít (1st person, future tense), abys to četl
They wanted you to read that = Chtěli (3rd person plural, past tense), abys to četl
We would like you to read that = Chtěli bychom (1st person plural, conditional), abys to četl
The translation of "I want you to read that" is "Chci, abys to četl"
"I want him to read that" = "Chci, aby to četl"
"I want her to read that" = "Chci, aby to četla"
"us, you (plural), them" = "abychom to četli, abyste to četli, aby to četli"
Note: Remember to always place a comma in front of "aby" in a sentence.
Future Tense
There are two ways to make future constructions in Czech - either by expressing the future tense in just one word by changing the verb (usually by adding a prefix and changing the stem), or by using the "to be" in future tense + infinitive construction. Here are some tips on what to use when:
1) Sometimes the choice depends on the particular verb. Some verbs require only one of the two possible ways to form future tense - e.g. the future tense of "I will go" is always "pojedu" (by car) or "půjdu" (on foot), never "budu jet", "budu jít".
2) Sometimes you can use both constructions with the same verb but with a slightly different meaning - e.g. "I will talk to him" = "Budu s ním mluvit" is a neutral way to say that you will be talking to someone, whereas "Promluvím si s ním" implies that you will be talking to someone about a particular thing, problem, etc.
3) And then there is the issue of the "verb aspect" ("slovesný vid" in Czech), which, as you correctly pointed out, has to do with the action described by the verb. There are two "verb aspects" in Czech - "dokonavý" (used for a one-time, finished action) and "nedokonavý" (used for a repeated or unfinished action). In most cases, the "dokonavý vid" uses the one-word future constructions, the "nedokonavý vid" uses the "to be" + infinitive future constructions. Examples:
"I will read a book next week" - "Příští týden BUDU ČÍST knihu" (over the course of the whole week, repeatedly, I don't know if I'll finish the book)
"I will read the article tonight" - "PŘEČTU si ten článek dnes večer" (I will read it from beginning to end)
"I will write a letter" - "BUDU PSÁT dopis" (doesn't specify over what time period and if I'll finish writing it) x "NAPÍŠU dopis" (I'll start and finish writing it)
"I will learn Czech" - "BUDU SE UČIT česky" (doesn't specify how advanced I'll become) x "NAUČÍM SE česky" (I'll learn Czech to the point when I don't have to continue learning it, I'll become fluent)
Possessives
Like in English, Czech has two ways to form possessives: by adding a possessive suffix (e.g. "Petrova kniha" - "Peter's book") or by declension ("Praha Karla Čtvrtého" - "Prague of Charles the Fourth"). I'm not sure what all the rules are that dictate when to use which - maybe someone else can help us here.
One rule is that you can only add a possessive suffix to a noun, and I think it always has to be in the singular. E.g. "Karlův most" but "Praha Karla Čtvrtého" (you can't add a possessive suffix to the numeral "Čtvrtý", so you have to use declension). You can say "bratrův dum" ("my brother's house") but you have to use declension if you want to use the possessive pronoun "můj" - "dům mého bratra" or use multiple words that describe your brother - "dům mého staršího bratra Petra". You can say both "profil hráče" and "hráčův profil", but only "profily hráčů" (plural).
As you can see, sometimes you can use either way to express possessiveness ("profil hráče", "hráčův profil") but in some cases one of the ways is a better choice (e.g. you could theoretically say "most Karla" instead of "Karlův most" but it would sound strange and clumsy).
[This message has been edited by Dana (edited May 14, 2003).]