I want to try it with someone IRL, but I am afraid, my only experience is with myself, in self bondage, I am afraid I just got too inside of my submission fantasies and make a mistake

Make that clear with them. Be honest and don't be afraid to step back if you've got a weird feeling in your gut, as well as don't be afraid to step forward and conquer your fears to live life and experience, experiment.

Buy your equipment, do your research, and be clear on boundaries, as well as wants - have a safe word at ALL TIMES.

Communication, you can never have too much communication. No matter if youre the sub or dom, talk about boundaries, expectations, the scene etc etc have safe words and safety tools around for cutting the rope in case something goes wrong. Think about safety plans for all the scenes.
Also do research online, theres a lot of good resources on how to practice safe bdsm and what to think about.
There’s also quite a few podcasts that might be interesting and helpful too

Try to enjoy yourself and have fun. Don't worry about trying to be the perfect dom/sub masochist/sadist. Like all forms of sex and sexual pleasure, what's important is that both you and your partner are comfortable and consenting :D