Hey Jacek, Im a fellow newbie so dont have too much advice but I can answer the pressure question - 15 bar seems to be standard across pretty much all thermoblock machines; temperature stability is more important than pressure as I understand it. From memory, somewhere in the vicinity of 80-90C is required, but thats the temperature of the water coming out of the group head not the final brew. Ive also found that pre-heating the cup with boiling water makes a huge difference to the final temperature with my cheapo Sunbeam machine.
The firmness of your tamp will probably have an effect on the end temperature, but someone more knowledgeable than me will be able to give you a better answer to that question. It definitely affects the time taken to pour the espresso - theres a golden rule along the lines of 30 seconds for 30mL of espresso, but thats assuming youre using single-walled coffee baskets rather than the double-walled ones that probably came with your machine (they have a second skin with only one hole that the coffee exits through and are a Very Bad Thing as I understand it).
In regard to how to make a coffee, youve made a good start coming to this site - Ive found people here to be very generous with their considerable knowledge of all things espresso :)
Also if you search through the old threads on this site youll find plenty of good info (Ive found searching with Google better than the built-in search tool though).
Anyway, as I said Im also new to the site so hopefully at least some of that advice is on the right track!