Greetings everyone.

I've searched lots of forums, but I could not find a proper one regarding this issue.

I've been studying Japanese at the university for a year now, and I can engage in basic/mid level conversations. I come from a country where being polite is also embodied in the language as well Turkey; Turkish. We have different verbs and pronouns for you - friend level (informal) and you - to someone higher than you in rank or age (polite). A bit similar to Japanese on that sense.

While I don't have a problem differentiating those in Japanese, I'm having a bit of an issue when it comes to relationships - be it just friendship or else. I basically can't read between the lines when it's appropriate for me to switch to casual form, unless someone explicitly tells me to do so.

For example, in Turkey we would just say "You don't have to speak in polite form to me" if we familiarize ourselves with the other person enough. That might be in 2 weeks or 2 hours, and it heavily depends on both sides.

It obviously differs a lot from person to person and from relationship to relationship. Considering two people are on "equal level" - age, school year, same company position etc - and they have been friends for some time, what would you reckon the appropriate time to be to switch the language usage? Would they always tell me to "feel comfortable and use informal tone"? Or should I search for clues? If I keep using informal language with someone, and the other person keeps on using the formal language, does that mean the other person would like to keep a distance between us so I should switch back, or he's just being extra polite?

Thanks for the read and answers

Ps: I'm studying at the Netherlands right now. Maybe someone might find that information relevant.