So I avoid unwanted conversations

The solution in my opinion is to do a couple things. Block them (as you mentioned) and report them to the italki administrators (obviously they have to have actually done something inappropriate), change your personal settings so that only people listed as friends can message you, and only use video calls on skype with people that you're pretty confident aren't going to act perverted. If you're unsure you can still talk through messages or by voice.

Alright, now that I know what you're trying to say I'm going to correct some grammar.

Has anyone else had bad experences here becouse of perverts that keep pestering you?

Italki is a wonderful tool for learning languages and learning about different cultures, making friends, having a fun time ... please, people with nasty intentions, get out of here (or simply "leave"). I can not stand it.

(well it is quite easy, just what you have to do is give your skype to another person who speak the lenguage what you want learn) I have no idea what you're trying to say here. 

I am talking about perverted people (or simply "perverts"). I know that the solution is to block them, but I still get really angry. I can't stand it.

I am talking about perverted. I know that the solution is block theme but I realy get angry, I can't stand it.

Yeah, I'm confused as well. Are you talking about perverts that act inappropriately, people who lie about their language abilities...?