"Should i "give" my soul to Satan before i start to talk with demons?"
You stated that English is not your first language, What I may think you mean could be entirely wrong, and trying to work that out, on-line, during Mercury Retrograde, Uh...
My experience as someone(relatively) new to the LHP is that Lord Satan does not collect souls the way some people collect sea shells or stamps. He does not want your soul. In fact, he will strongly encourage you to keep it close at hand so that YOU can do very important work on your own spiritual growth. If you find mantras useful, and many people on many different Paths do, one I would encourage you to use when considering working with Demons, or Lord Satan directly is..."Be Respectful" ALWAYS! Every. Time.
Demons do not have to work with humans. Talk to those here on the board who have DC's (Demon Companions) They will tell that their DC's work with them because they have freely chosen to do so. There is no cosmic law that says they have to work with us. And if they don't wanna, they won't. If interacting with Demons was as effortless as the movies and TV make it out to be, I'd be on Cloud Nine!

My own personal interaction with Lord Satan was brief, but direct. And I am certain that the only reason that it happened was that I approached him with a question that was coming from a sincere and respectful space.
Learning, any learning, is a process. There are no deadlines you have to meet on the LHP. It's your soul that is evolving, growing, expanding. You do so at your own rate. Your life is your path. You, and you alone, chose what you will, or will not do over the course of that life. If you chose growth, exercising free will and serious learning, there are some truly Righteous beings who will glad to lend a hand. More than a few are on this board
Stick around, hang out, and Ask Questions. There are tons of folks happy to answer. You might even have fun!
