Most sessions on slot machines will result in losing money, and there's nothing you can do to chance that. Sometimes you'll win at slots, and even win big. Enjoy those times when they come. But never bet money you can't afford to lose, and be sure you're playing games that fit your bankroll.
In most slots, the rate is somewhere between 80% and 95%, but some games can exceed 95%. The basics of the return to player percentage indicate that if you betR$100 on a game with an RTP of 94%, you'll win backR$94. But again, this is for long-term results since the rate was determined over millions of spins.