How many cities do you recomend I build ? I would like to have a balance between "enough" and "turn takes too long". What would you say is the amount one should have at least ?
One well placed city is often "enough," in the sense that people can win the One City Challenge. Civ size is largely a matter of preference (although from a strict in-game sense, more cities are usually better). Something to keep in mind is the Riot Factor (extra unhappiness from having too many cities). At deity level (and Large Map), a Democracy can have 15 cities and still have the first citizen content by default. After that, the first citizen is unhappy, which makes celebration more difficult (and requires either HG/CfC or courthouses for odd sized cities). After 30 cities, you will start getting "black hats" (very unhappy citizens) which can be made happy with only 2 luxuries, thus making it easier to have celebrations in the city. At 45 cities, all your cities will have one black hat.
Also the trade with Japan started very well but then they sneak attack on my caravans. How do i handle this ? Whats the best way to still get my caravans going ? (Conquer them, and reduce to 2-3 cities, but then they get small right ?)
Try to avoid having too many caravans on the ground at the same time; take them by ship as far as possible. You can also consider building (or capturing) a "port city" where you could unload and protect caravans. Keep an eye on attitude; the better their attitude, the less likely they are to attack. Also, consider giving tech gifts from time to time to improve their attitude (and give them things that might make them better trading partners, such as Republic and Construction).
Conquering a large portion of the Japanese civ probably won't do you much good; I wouldn't take more than a couple cities before you establish trade routes to other places.
I have Marco Polo now, im supreme so my KeyCiv are the purple in my case Mongols, right ? It seems they are pretty far behind technologie wise, how do i know if i should tech bomb them or not ?
At the moment you probably don't have many techs that are dangerous for the Mongols to have. Giving away a lot of techs will probably improve relations, and lower research costs. Lower research costs are always good, unless you are running into the 2/3 delivery cap (delivery bonuses are either capped at about 200 or 2/3 of your science cost). If you are conducting most research by caravan delivery, a higher cost may not be a problem, but at this point, there is little need to keep techs from the Mongols.
EDIT: Okey I started over again at 250 b.c. I know you guys normally dont do this but im learning here and right now I wanna improve not live with my mistakes. So I realized that the Japanese sneak attack probably was because I allied with Spain against the Mongols and the Mongols were allied with the Japanese. So Japanese and Mongols teamed up against me... those sneaky bastards
We only care if you re-load in a competition. You can learn a lot from re-loading, in particular it is worth while to check the different payouts from trade deliveries.
So the question I have now, if someone like in my case the Spanish come and ask me for war against an unknown Civ. I usually tended to agree since they wont bother me anyway(too far away and dumb ai). And I get a better standing with the Civ I allied with. Now with Trade in the Picture that was obviously bad. What do you do if you dont have the relations in mind when they ask ?? Or do you never agree anyway ??
Before entering into an alliance, think about what you expect to get out of it. If you are weak, you might be able to get some gifts from your ally, but you will be expected to give gifts if you are strong. You are protected from sneak attacks by your ally as well, you can move through his territory, and you may get military help (of dubious quality) in the event of war.
On the downside, if/when the alliance is cancelled, you will have units re-located (particularly devastating for ship chains and explorers) if they are nearer your former ally's city than your own.
Interestingly, alliances don't change the "reputation rules" (although they will impact the attitude of your ally) for declaring war. That is, you still take a reputation hit for declaring war at the request of your ally (but not so large a hit as if you declared war yourself), but you don't get a hit for refusing to aid your ally. Just be aware that they might not help you in the future.
If you declare war on someone you haven't met, there is no reputation hit, but they won't be very happy with you when you do meet.
And still, what to do if a sneak attack from the trade partner comes anyway ?
Minimizing your risk from sneak attacks is something you just have to do. If you have to leave multiple caravans in the open, be mindful of your partner's attitude. If they keep making demands of you, and have a negative attitude, you may want to consider finding another partner.