It depends on languistic function and context to understand its meaning.
Trông:
• wait for/ look forward to something ( trông mong, trông chờ...)
• look at something (Trông kìa = nhìn kìa)
• look after somebody ( trông nom)
Trong:
• if being an adjective, it mean pure, fresh.
ex: fresh air, pure water
• If being a preposition, it mean in, under somewhere to refer inside of a place.
ex: under his room ( trong phòng anh ấy)
>> I am also learning English, so I hope you give me more opinions to improve English together.. Thanks :)