Me ducho en el baño means in English: I take a shower in the bathroom.
"Me ducho a las ocho" is grammatically correct but it is incoherent as an answer to the question "Where do you take a shower". It would be correct if the question was "¿Cuándo te duchas?" o "¿A qué hora te duchas?"
"Me ducho en la cocina" is wrong as the kitchen is not a suitable place to take a shower.
"Te duchas en el baño" is also incorrect because the question is aimed at me (where do YOU take a shower?). Answering with "te" would be correct if the question was "Where do I take a shower?"
