In module 1.8, phrases are given such as, "Sushi wa suki desu ka?" and, "O-sushi o tabemasu."
What is the point of choosing "wa" over "o"?
I get that "o" is the particle that defines the word before it as the object of the verb that follows. I also get that "wa" defines the topic, creates context, and may be translated like "speaking of ______." But my neural pathways seem to have suddenly broken down when it comes to the reasoning as to why, at least with some of these examples, I would opt for "wa" rather than "o".
For example, I choose the "o" in the latter statement of "O-sushi o tabemasu" because sushi is the object of eating, but, in the former example, isn't sushi the object that is being liked?
In a similar way, consider the statements from Module 1.4: "Anata wa nihongo ga hanasemasu ka?" and, "Dure gurai nihongo o benkyo shite imasu ka?"
"o" is being used in the latter example because "nihongo" is the object of studying. How come, then, in the former example, "ga" is used rather than "o" which would show that "nihongo" is the object of speaking?
In the former example, should "o" never be there at all, or does the "ga" for some reason take priority?
Thank you much!