I believe that, actually, the sentence is about being able to "speak Spanish."
In addition, I know Spanish when I hear it, even if I don't understand it.
I can read Spanish (and "know" Spanish in that respect), but am not very good at talking in Spanish (speaking Spanish).
I would like to be more able to speak Spanish, as my ability is weak.
Many people "know" something in theory, without being able to perform it.
Two different verbs, in fact you are misusing the word ''try'' (though this is very common, possibly because it is much simpler to say than ''be able to''). In Spanish, French and other languages, the concepts are more defined. Poder relates to ability and possibility and as duggg said, power, just as pouvoir does in French and both are irregular (it's a Latin thing). It's a good word for translating ''might'', as in ''that might happen'' - ''eso podría pasar''. Whereas to try really means to attempt, to test, if at first you don't succeed, try, try again. You wouldn't use ''poder'' to translate it into Spanish.
There is no limit, grammatically, but the sentence would usually end up hard to understand with more than 3 stacked infinitives, though it would still be valid. Solo tienes que querer tratar de aprender a necesitar ir a hablar con gente confusa. You just have to want to try to learn to need to go to talk to confusing people.