There aren't really general answers to any of those -- chess is a hard game :-(
General Rules in Chess

I need general answers. like a bisschop is better in an open game position than a horse and viceversa. Or a knight is best placed in front of a view pawns.'..
Those sort of things. Are there really no general answers possible?

general rule #1: do not refer to knights as "horses"
EDIT:
okay, being serious:
in general, bishops are better in open games and endgames. knights are better in closed games. obviously this is in general and not always the case.
what side to attack really doesn't have a general rule. it greatly depends on piece placement.
in general, i can't even think of any time that doubled pawns are good except if it's in a situation in which you are capturing an opponent's minor piece or something along those lines. the doubled pawns are still not "good" in this situation, but well worth the material gain.
in general, rooks are best on open files (no pawns in the way) or half open files (one pawn in the way). rooks become even stronger on when they are on the 7th rank (if you are white) or the 2nd rank (if you are black)
in general, bishops are best on the open long diagonals.
in general, knights are best in the center of the board because they can attack the most squares there. also, when supported by a pawn on a weak square they become very strong. a weak square is a square that your opponent cannot (easily) defend.

haha. i'm sorry. in the netherlands we call a knight 'paard'. The direct translation is horse. That's where the mistake comes from. Thanks for noticing.

Really depends on where you are in your chess strength. If your playing strength is <1300-1400 USCF (or ELO for that matter), then following guidelines "blindly" is surprisingly a good thing.
You need to crawl before you learn to walk.
What makes the stronger players strong is their ability to discern when "natural" guideline-abiding moves make sense and when they don't. My former coach used to call out dubious moves by me by saying "That's the kind of move either a beginner would make or a Grandmaster". :)
So ASSUMING your current rating MATCHES playing strength => you are indeed looking for guidelines THEN your questions are answered thus:
Q. when is a bishop better than a Knight?
A. When it has more squares to dominate over. Usually long diagonals which are prominent in "open" positions. Endgames usually tend to favor bishops because they move around an emptier board faster.
Q. What side of the board should an attack be aimed to? It depends on what? Pawn structure? Pieces Minority??
A. Usually the direction pointed to by your pawns, assuming you have a fixed pawn center. For e.g. FIXED white pawns on d4 and e5 imply a Kingside attack as the pawns are pointing that-a-ways. Though a more general answer is => you attack where you see a weakness or where you can create a weakness....plain and simple. If you cannot see or create a weakness, you have NO BUSINESS attacking and should be improving each of your pieces or better yet, covering up any weaknesses on your end.
Q. When are doubled pawns good or bad?
A. In general => Doubled pawns are worst when they are isolated doubled pawns. For example a capture such as Bxa3 answered by bxa3 leaves isolated doubled pawns on the a-file. They can be good if the file that is obviously opened can yield advantages or if you want to control certain central squares with your doubled-pawns. Once again => these are just guidelines.
Q. What are the best places for a knight (or rook or bisschop)?
A.Too general to give you specific guidelines here..but still => Knights love outposts. Bishops love long diagonals. Rooks like open files and love getting onto your opponent's 1st/2nd ranks. (the 2nd is more commmon).
Caveat => A guideline is a guideline, not a rule. You will start to LEARN when to apply it and when not to. For example => Doubling and isolating pawns may open up the g-file for my rook that could launch a lethal attack against a weak enemy king.
Even worse is when you start using tie-break criterion like guidelines in non-tiebreak positions. For example, if you are up material, one fundamental strategy that almost always applies is to trade pieces (not pawns). But in such a position, If by trading, you end up doubling or isolating pawns, and thus, decide NOT TO TRADE, you're just being silly following guidelines ("Doubled/Isolated pawns are bad!" blindly.
You have been warned :)

in general, i can't even think of any time that doubled pawns are good except if it's in a situation in which you are capturing an opponent's minor piece or something along those lines. the doubled pawns are still not "good" in this situation, but well worth t
Well, I'm a bit strange in this respect. Sometimes in the French or Nimzo White gets doubled c pawns. For some reason, I really like this setup for white.
My theory goes something like this: often in this type of position, c4 is a really good move. With doubled c pawns, you can play it twice...

As others have mentioned bishops tend to be better than knights in endgames. However, if all the pawns are on one side of the board, then a knight's ability to attack squares of both colors makes it better. But bishops are definitely better in endgames with pawns on opposite ends of the board, since it can move back and forth easily.

Just call it a horsie, and then you'll probably win money from the street hustler.
haha. not funny anymore! i told you were it came from.
See it on the bright side: you learnt the dutch translation for knight. Isn't that great!

Just call it a horsie, and then you'll probably win money from the street hustler.
haha. not funny anymore! i told you were it came from.
See it on the bright side: you learnt the dutch translation for knight. Isn't that great!
He wasn't making fun of you. A lot of beginners or non-chess players who speak English call it a horse. Saying that in front of someone who hustles chess games for money on the street is a great way to get them to underestimate you.

Just call it a horsie, and then you'll probably win money from the street hustler.
haha. not funny anymore! i told you were it came from.
See it on the bright side: you learnt the dutch translation for knight. Isn't that great!
He wasn't making fun of you. A lot of beginners or non-chess players who speak English call it a horse. Saying that in front of someone who hustles chess games for money on the street is a great way to get them to underestimate you.
That makes sense. I was a little bit offended, because I know it's a knight instead of a horse, it was a one time mistake.
I'm sorry for offending you ozzie

Hi Wesley, nice to see another dutch chess player.
You asked for general rules. I want to advice to read a good beginners chess book. Dont take it as a noffence! I am also doing it myself because I want to learn new things and get new idea's and methods. When you read about the general rules the book shows you a lot of examples of situations so you will see why this is a good rule.
I want to add a rule to your list. When you are a beginner, always castle. ( rokeren in dutch). When possible ,castle kingside. Then you king is protected and your kingside rook is active in the middle of the board.

btw, what do you mean when talking about 'street players'? I think it's not meant literally. But what are they, just friendly games of chess?

I'm talking about guys who set up boards at cafes or on boardwalks or other outside areas, who play for money. Their typical strength is about A-player, maybe low expert, sometimes a bit of an aggressive B player.

haha. i'm sorry. in the netherlands we call a knight 'paard'. The direct translation is horse. That's where the mistake comes from. Thanks for noticing.
That's hilarious. My dad, who was a youth champion of The Netherlands a few years back still calls the knight a "horse", and the bishops "advisors".

The answers to these questions are the topic of the books written on chess. The complexity of the answers is the reason there is more literature on the game of chess than any other game in the history of human civilization.

haha. i'm sorry. in the netherlands we call a knight 'paard'. The direct translation is horse. That's where the mistake comes from. Thanks for noticing.
That's hilarious. My dad, who was a youth champion of The Netherlands a few years back still calls the knight a "horse", and the bishops "advisors".
Where does advisors come from? the translation is 'lopers'. Translated they are 'walkers', so could you please ask him where advisors come from?
What general rules are known in chess? The goal I'm aiming for are things that are inportant to know in every situation.
Things like:
-when is a bisschop better than a horse?
- What side of the board should an attack be aimed to? It depends on what? Pawn structure? Pieces Minority??
- When are doubled pawns good or bad?
- What are the best places for a knight (or rook or bisschop)?
Of course other hints are welcome to. Hope you can help me with understanding those general rules in chess.
Thank you!