Welcome to the LL forum! No problem with the language - you're much better at English than I'm sure I am in your native language! :-)
I don't know much about Photoshop Elements, but am a big user of Photoshop. If the raw converter in PSE is the same as the one in PS, then it's one of the top raw converters, and you don't need anything else. (Some people prefer it to the other "big" ones, others prefer one or the other of the other converters, but it's definitely one of the "big" ones). Hopefully someone else here can comment on whether the converters in PSE and PS are the same or not...
Does PSE have the Channel Mixer in its menus? If so, then that's the best way in PSE to convert to B&W. You click the check box at the bottom of the Channel Mixer window that makes it monochrome, then adjust the three color channels in whatever proportion you want to give you a B&W image. If PSE doesn't have the Channel Mixer and you're serious about B&W photography, you should consider upgrading from PSE to PS.
There are also some third-party Photoshop plug-in programs that convert to B&W that a lot of people like (and which no doubt other people here will tell you about), but I don't know whether they will work with Elements.
Lisa