1. hows the mining bitcoin works?
Using mining software you hash blocks to see if that block contains bitcoins
2. how much is the profit ? is it worth making a miner?
Depends on if your soloing or pooling, but right now each block contains 50btc but that will change. If you find a good pool with a good hashing powers and you have a lot of GPU's sitting around then go for it.
3. got any guide how to ? do it ? what specs? of comp need? minimum comps?
really depends on what you are doing. Google is your friend