No, we exclusively use på for thinking about things. tänka om is another particle verb that means to rethink or to reconsider, and which is intransitive, unlike in English.
Is there a way I would know the speaker said "det" instead of "dig"? I put "dig" and got it wrong.
It has a slightly different meaning, and is hard to translate into Swedish.
Though "will" can mean "want", it's probably a terrible idea in a language course to accept it as a translation of vill, which in Swedish always expresses desire.
So, I confused some Swedes when I told that after two hours of talking to them all, "Nu, tänker jag på svenska. Vanligtvis tänker jag på engelska och sedan översätter jag." They understood after a bit, but I now realise that it sounded like I was saying "I think ABOUT Swedish. Normally I think about English and then translate." What I meant to say was "Now, I thinking IN Swedish. Normally I think in English and then translate." So, my question is, if "tänker på = "think about", what would the phrase for "I am starting to think in Swedish more often." or, for another example "His Spanish is good enough that he thinks in Spanish rather than translating." ? Thanks guys.
Actually, what you said is absolutely fine. In fact, I'd say it's exactly how I'd phrase it as well. It's perfectly natural and it's not your fault if they didn't understand it.
Oh ok, it could have been pronunciation or a few other things, including being in a small concrete room with 100 other people. So, how would you say "I often think ABOUT Swedish." (because I do that too haha) Maybe you could phrase it in the equivalent way of like "I have Swedish on my mind." or something?
Jag tänker på svenska is totally ok for thinking about the Swedish language, but it is a bit abstract. It might be more natural to come right out and say that you're thinking about svensk grammatik, hur svenska fungerar or something more concrete. In general, the more interested you are, the more specific you tend to be.
With no context, jag tänker på svenska can mean either 'I'm thinking in Swedish', 'It's Swedish that I have in mind', or 'I'm thinking about Swedish, the language', but the first two are the most likely.
I'd actually use Jag tänker ofta på svenska for that as well - same stress and prosody and everything.