"Where are you going ?" / "Куда ты идешь?"
"I'm going to the lake." / "Я иду к озеру."
"Are you going to bath ?" / "Ты собираешься купаться?"
"Yes, I'm going to bath." / "Да, я собираюсь купаться."
"Are you going often to the lake ?" / "Ты часто ходишь к озеру?"
"Yes, I go there often because I really love to bath" / "Да, я часто хожу туда, потому что очень люблю купаться."
"Do you also bath in that lake in winter ?" / "Зимой ты тоже купаешься в этом озере?"
"Of course, I also bath in winter !" / "Конечно, зимой я тоже купаюсь!"
This translation may differ from what your teacher is expecting to see though, because I don't know exactly what you must know about Russian language already. For example, native Russian would say "Я иду на озеро" instead of "Я иду к озеру". The semantic difference is quite subtle: if someone says he goes "к озеру" it means that he use the lake as a checkpoint on his way and "на озеро" means that he's going to stay on the lake for a while, and I'm not sure you even have to know such difference from your training programme.
Also, bathing in lake in winter in Russia... C'mon, you're joking!:lol: Is Katia a 'walrus' (as we call ice-swimmers)?